Intel® Celeron® D Processor in
the 775-Land LGA Package for
Embedded Applications
Thermal Design Guide
July 2005
Order #303730-002
Contents
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Celeron® D Processor in the 775-Land LGA Package for Embedded Applications may contain design defects or errors known as errata
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Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide
Order #303730
Contents
Contents
1.0 Introduction....................................................................................................................................6
1.1 Document Goals and Scope.................................................................................................6
1.1.1 Importance of Thermal Management.......................................................................6
1.1.2 Document Goals......................................................................................................6
1.1.3 Document Scope.....................................................................................................6
1.2 References ...........................................................................................................................7
1.3 Terms and Definitions...........................................................................................................7
2.0 Processor Thermal/Mechanical Information...............................................................................9
2.1 Mechanical Requirements ........................................................... .... ... ... ... .... ... .....................9
2.1.1 Processor Package..................................................................................................9
2.1.2 Heatsink Attach......................................................................................................10
2.1.2.1 General Guidelines................................................................................10
2.1.2.2 Heatsink Clip Load Requirement................................. .... ......................11
2.1.2.3 Additional Guidelines.............................................................................11
2.2 Thermal Requirements .......................................................................................................11
2.2.1 Processor Case Temperature and Power Dissipation...........................................12
2.2.2 Thermal Profile ......................................................................................................12
2.2.3 T
2.3 Heatsink Design Considerations.........................................................................................14
2.3.1 Heatsink Size.........................................................................................................15
2.3.2 Heatsink Mass.......................................................................................................15
2.3.3 Package IHS Flatness...........................................................................................15
2.3.4 Thermal Interface Material.............. ... .... ...................................... .... ... ... ... ... .... ... ...16
2.3.5 Summary ...............................................................................................................16
2.4 System Thermal Solution Considerations........... ... ... ... .... ... ... ... ....... ... ... ... .... ... ... ... ... .... ... ...16
2.4.1 Improving Chassis Thermal Performance..............................................................16
CONTROL
...............................................................................................................13
3.0 Thermal Metrology ......................................................................................................................18
3.1 Characterizing Cooling Performance Requirements ..........................................................18
3.1.1 Example.................................................................................................................19
3.2 Processor Thermal Solution Performance Assessment .....................................................20
3.3 Local Ambient Temperature Measurement Guidelines ......................................................20
3.3.1 Measuring Active Heatsinks ............................... ... ... ... ... .... ... ................................20
3.3.2 Measuring Passive Heatsinks................ ................................................................21
3.4 Processor Case Temperature Measurement Guidelines....................................................22
4.0 Thermal Management Logic and Thermal Monitor ..................................................................23
4.1 Processor Power Dissipation..............................................................................................23
4.2 Thermal Monitor Implementation........................................................................................23
4.2.1 PROCHOT# Signal................... ... ... ... .... ... ... ....................................... ... ... ... .... ... ...23
4.2.2 Thermal Control Circuit..........................................................................................24
4.2.3 Operation and Configuration.............. .... ... ... ... .... ... ...................................... .... ... ...25
4.2.4 On-Demand Mode.................................................................................................25
4.2.5 System Considerations.......................................................... ... ... .... ... ... ... .............26
4.2.6 Operating System and Application Software Considerations ................................26
4.2.7 On-Die Thermal Diode........................... ... ... ... .... ...................................... ... .... ... ...26
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide 3
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Contents
4.2.7.1 Reading the On-Die Thermal Diode Interface........................................27
4.2.7.2 Correction Factors for the On-Die Thermal Diode.................................27
4.2.8 THERMTRIP# Signal.............................................................................................28
4.2.8.1 Cooling System Failure Warning...........................................................28
4.2.9 How On-Die Thermal Diode, TCONTROL and Thermal Profile Work Together....29
4.2.9.1 On-Die Thermal Diode Less than TCONTROL......................................29
4.2.9.2 On-Die Thermal Diode Greater than TCONTROL.................................29
4.3 Acoustic Fan Speed Control........... ....................................... ... ... ... .... ... ... ..........................29
5.0 Intel Enabled Thermal Solutions................................................................................................30
5.1 Thermal Solution Requirements.........................................................................................30
5.2 ATX Form Factor................................................................................................................31
5.3 1U Form Factor............................... ... ... .... ...................................... .... ... ... ... .... ... ................31
5.4 2U Form Factor............................... ... ... .... ...................................... .... ... ... ... .... ... ................33
5.5 Reference Thermal Mechanical Solution............................................................................35
6.0 Conclusion...................................................................................................................................36
A LGA775 Socket Heatsink Loading.............................................................................................37
B Heatsink Clip Load Metrology....................................................................................................42
C Thermal Interface Management..................................................................................................46
D Case Temperature Reference Methodology.............................................................................47
E Board Level PWM and Fan Speed Control Requirements.......................................................57
F Mechanical Drawings..................................................................................................................58
G Vendor Information .....................................................................................................................64
Figures
1 Package IHS Load Areas .............................................................................................................9
2 Processor Case Temperature Measurement Location...............................................................12
3 Example Thermal Profile............................................................................................................13
4 Processor Thermal Characterization Parameter Relationships..................................................19
5 Measuring T
6 Measuring T
7 Concept for Clocks under Thermal Monitor Control ...................................................................24
8 Thermal Characterization Parameters for Various Operating Conditions ..................................31
9 1U Copper Heatsink ...................................................................................................................32
10 1U Thermal Solution Z-Height Constraints.................................................................................33
11 2U Copper Heatsink ...................................................................................................................33
12 Case-to-Ambient Thermal Characterization Parameter Ψ
13 2U Height Restrictions................................................................................................................35
14 Board Deflection Definition..................... ... ... .... ... ... ... .... ...................................... .... ... ... ... ..........38
15 Example: Defining Heatsink Preload Meeting Board Deflection Limit........................................40
16 Load Cell Installation in Machined Heatsink Base Pocket – Bottom View .................................43
17 Load Cell Installation in Machined Heatsink Base Pocket – Side View......................................43
18 Preload Test Configuration.........................................................................................................44
— Active Heatsink...............................................................................................21
LA
— Passive Heatsink............................................................................................22
LA
(°C/W)............................. ... ... .... ...34
CA
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Contents
19 FC-LGA4 Package Reference Groove Drawing.........................................................................49
20 IHS Reference Groove on the FC-LGA4 Package .....................................................................50
21 IHS Groove Orientation Relative to the LGA775 Socket............................................................50
22 Bending the Tip of the Thermocouple.........................................................................................51
23 Securing Thermocouple Wires with Kapton* Tape Prior to Attach.............................................51
24 Thermocouple Bead Placement (View 1)...................................................................................52
25 Thermocouple Bead Placement (View 2)...................................................................................52
26 Position Bead on Groove Step ...................................................................................................53
27 Detailed Thermocouple Bead Placement...................................................................................53
28 Using 3D Micromanipulator to Secure Bead Location................................................................54
29 Measuring Resistance between Thermocouple and IHS............................................................54
30 Applying the Adhesive on the Thermocouple Bead....................................................................55
31 Thermocouple Wire Management in the Groove........................................................................55
32 Removing Excess Adhesive from IHS........................................................................................56
33 Filling the Groove with Adhesive ................................................................................................56
34 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 1.............................................................................................59
35 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 2.............................................................................................60
36 ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 3.............................................................................................61
37 1U/2U Motherboard Component Keep-In Definition, Primary Side ............................................62
38 1U/2U Motherboard Component Keep-In Definition, Secondary Side........................................63
Tables
1 Reference Documents..................................................................................................................7
2 Terms and Definitions...................................................................................................................7
3 Thermal Diode Interface.............................................................................................................27
4 Thermal Characterization Parameter at Various TLA Levels .....................................................30
5 Enabled Thermal Solutions............................ ... ... ... .... ...................................... .... ... ... ... ... .... ......31
6 Board Deflection Configuration Definitions.................................................................................38
7 Typical Test Equipment..............................................................................................................44
8 Definitions...................................................................................................................................47
9 Supporting Test Equipment........................................................................................................47
10 Mechanical Drawings..................................................................................................................58
11 Intel Reference Component Thermal Solution Provider.......................................................... ...64
Revision History
Date Revision Description
July 2005 002 Updated Table 1 and Table 4.
September 2004 001 Changes to branding. First public release.
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide 5
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Introduction
1.0 Introduction
1.1 Document Goals and Scope
1.1.1 Importance of Thermal Management
The objective of thermal management is to ensure that the temperatures of all components in a
system are maintained within their functional temperature range. Within this temperature range, a
component is expected to meet its specified performance. Operation outside the functional
temperature range can degrade system performance, cause logic errors or cause component and/or
system damage. Temperatures exceeding the maximum operating limit of a component may result
in irreversible changes in the operating characteristics of this component.
In a system environment, the processor temperature is a function of both system and component
thermal characteristics. The system level thermal constraints consist of the local ambient air
temperature and airflow over the processor as well as the physical constraints at and above the
processor. The processor temperature depends in particular on the component power dissipation,
the processor package thermal characteristics, and the processor thermal solution.
All of these parameters are affected by the continued push of technology to increase processor
performance levels (higher operating speeds, GHz) and packaging density (more transistors). As
operating frequencies increase and packaging size decreases, the power density increases while the
thermal solution space and airflow typically become more constrained or remains the same within
the system. The result is an increased importance on system design to ensure that thermal design
requirements are met for each component, including the processor, in the system.
1.1.2 Document Goals
Depending on the type of system and chassis characteristics, new system and component designs
may be required to provide adequate cooling for the processor. The goal of this Thermal Design
Guide is to provide an understanding of these thermal characteristics and discuss guidelines for
meeting the thermal requirements imposed on single processor systems for the Intel
Processor in the 775-Land LGA Package for Embedded Applications. The specifications for this
processor (also referred to herein as the Intel Celeron D Processor in the 775-Land LGA Package)
are delineated in the Intel
1.1.3 Document Scope
This document discusses the thermal management techniques for the Intel Celeron D Processor in
the 775-Land Package.
The processor physical dimensions and thermal specifications used in this document are for
illustration only. Refer to the Intel Celeron D Processor in the 775-Land Package Datasheet for
product dimensions, thermal power dissipation and maximum case temperature. In case of conflict,
the datasheet supersedes this document.
®
Celeron® D
®
Celeron® D Processor in the 775-Land LGA Package Datasheet.
6 Intel
®
Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide
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1.2 References
Material and concepts available in the following documents may be beneficial when reading this
document.
Table 1. Reference Documents
Fan Specification for 4 Wire PWM Controlled Fans
®
Intel
Celeron® D Processors 3xx Sequence Datasheet on 90nm Process
in 775-Land Package
Intel® Pentium® 4 Processor 570/571, 560/561, 550/551, 540/541, 530/531
and 520/521 Supporting Hyper-Threading Technology Datasheet
®
Intel
Pentium® 4 Processor on 90 nm Process in the 775-Land LGA
Package Thermal Design Guide
LGA775 Socket Mechanical Design Guide Intel document #302666
Performance ATX Desktop System Thermal Design Suggestions http://www.formfactors.org/
Performance microATX Desktop System Thermal Design Suggestions http://www.formfactors.org/
Server System Infrastructure Thin Electronics Bay Specifications http://www.ssiforum.org/
Introduction
Document Comment
http://www.formfactors.org/dev
eloper%5Cspecs%5CREV1_2_
Public.pdf
Intel document #304092
Intel document # 302351
Intel document #302553
1.3 Terms and Definitions
Table 2. Terms and Definitions (Sheet 1 of 2)
Term Description
T
A
T
C
T
E
T
S
T
C-MAX
Ψ
CA
Ψ
CS
Ψ
SA
The measured ambient temperature locally surrounding the processor. The ambient
temperature should be measured just upstream of a passive heatsink or at the fan inlet
for an active heatsink. Also referred to as T
The case temperature of the processor, measured at the geometric center of the topside
of the IHS.
The ambient air temperature external to a system chassis. This temperature is usually
measured at the chassis air inlets.
Heatsink temperature measured on the underside of the heatsink base, at a location
corresponding to
The maximum case temperature as specified in a component specification.
Case-to-ambient thermal characterization parameter (psi). A measure of thermal
solution performance using total package power. Defined as (T
Power.
NOTE: Heat source must be specified for
Case-to-sink thermal characterization parameter. A measure of thermal interface
material performance using total package power. Defined as (T
Power.
NOTE: Heat source must be specified for
Sink-to-ambient thermal characterization parameter. A measure of heatsink thermal
performance using total package power. Defined as (T
NOTE: Heat source must be specified for
T
C.
LA
Ψ measurements.
Ψ measurements.
– TA) / Total Package Power.
Ψ measurements.
S
– TA) / Total Package
C
– TS) / Total Package
C
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide7
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Introduction
Table 2. Terms and Definitions (Sheet 2 of 2)
TIM
P
MAX
TDP
IHS
LGA775 Socket
ACPI Advanced Configuration and Power Interface.
Bypass
FMB
Thermal Monitor
TCC
T
DIODE
FSC
T
CONTROL_BASE
T
CONTROL_OFFSET
T
CONTROL
PWM
Health Monitor
Component
U
Thermal Interface Material: The thermally conductive compound between the heatsink
and the processor case. This material fills the air gaps and voids, and enhances the
transfer of the heat from the processor case to the heatsink.
The maximum power dissipated by a semiconductor component.
Thermal Design Power: a power dissipation target based on worst-case applications.
Thermal solutions should be designed to dissipate the thermal design power.
Integrated Heat Spreader: a thermally conductive lid integrated into a processor
package to improve heat transfer to a thermal solution through heat spreading.
The surface mount socket designed to accept the Intel Celeron D Processor in the
775-Land LGA Package.
Bypass is the area between a passive heatsink and any object that can act to form a
duct. For this example, it can be expressed as a dimension away from the outside
dimension of the fins to the nearest surface.
Flexible Motherboard Guideline: an estimate of the maximum value of a processor
specification over certain time periods. System designers should meet the FMB values
to ensure their systems are compatible with future processor releases. FMB1 and FMB2
are sequential estimates of processor specifications over time.
A feature on the Intel Celeron D Processor in the 775-Land LGA Package that attempts
to keep the processor’s die temperature within factory specifications.
Thermal Control Circuit: Thermal Monitor uses the TCC to reduce die temperature by
lowering effective processor frequency when the die temperature is very near its
operating limits.
Temperature reported from the on-die thermal diode.
Fan Speed Control: Thermal solution that includes a variable fan speed which is driven
by a PWM signal and uses the on-die thermal diode as a reference to change the duty
cycle of the PWM signal.
Constant from the processor EMTS that is added to the T
in the value for
Value read by the BIOS from a processor MSR and added to the T
results in the value for
T
CONTROL
Pulse width modulation is a method of controlling a variable speed fan. The enabled 4
wire fans use the PWM duty cycle % from the fan speed controller to modulate the fan
speed.
Any standalone or integrated component that is capable of reading the processor
temperature and providing the PWM signal to the 4 pin fan header.
A unit of measure used to define server rack spacing height. 1U is equal to 1.75 inches,
2U equals 3.50 inches, etc.
is the specification limit for use with the on-die thermal diode.
T
CONTROL
T
CONTROL
CONTROL_OFFSET
CONTROL_BASE
that results
that
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Processor Thermal/Mechanical Information
2.0 Processor Thermal/Mechanical Information
2.1 Mechanical Requirements
2.1.1 Processor Package
The Celeron D Processor in the 775-Land LGA Package is packaged in a Flip-Chip Land Grid
Array (FC-LGA4) package that interfaces with the motherboard via a LGA775 socket. Please refer
to the processor datasheet for detailed mechanical specifications.
The processor connects to the motherboard through a land grid array (LGA) surface mount socket.
The socket contains 775 contacts arrayed about a cavity in the center of the socket with solder balls
for surface mounting to the motherboard. The socket is named LGA775 socket. A description of
the socket can be found in the LGA775 Socket Mechanical Design Guide.
The package includes an integrated heat spreader (IHS) that is shown in Figure 1 for illustration
only. Refer to the processor datasheet for further information. In case of conflict, the package
dimensions in the processor datasheet supercede dimensions provided in this document.
Figure 1. Package IHS Load Areas
Top Surface of IHS
Substrate
Substrate
The primary function of the IHS is to transfer the non-uniform heat distribution from the die to the
top of the IHS, out of which the heat flux is more uniform and spread over a larger surface area (not
the entire IHS area). This allows more efficient heat transfer out of the package to an attached
cooling device. The top surface of the IHS is designed to be the interface for contacting a heatsink.
Top Surface of IHS
to install a heatsink
to install a heatsink
IH S Step
IH S Step
to in te rface wi th LGA775
to in te rface wi th LGA775
Socket Load P late
Socket Load P late
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide9
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Processor Thermal/Mechanical Information
The IHS also features a step that interfaces with the LGA775 socket load plate, as described in
LGA775 Socket Mechanical Design Guide. The load from the load plate is distributed across two
sides of the package onto a step on each side of the IHS. It is then distributed by the package across
all of the contacts. When correctly actuated, the top surface of the IHS is above the load plate
allowing proper installation of a heatsink on the top surface of the IHS. The post-actuated seating
plane of the package is flush with the seating plane of the socket. Package movement during socket
actuation is along the Z direction (perpendicular to substrate) only. Refer to the LGA775 Socket
Mechanical Design Guide for further information about the LGA775 socket.
The processor datasheet gives details on the IHS geometry and tolerances, and IHS material.
The processor package has mechanical load limits that are specified in the processor datasheet. The
specified maximum static and dynamic load limits should not be exceeded during their respective
stress conditions. These include heatsink installation, removal, mechanical stress testing, and
standard shipping conditions.
• When a compressive static load is necessary to ensure thermal performance of the thermal
interface material (TIM) between the heatsink base and the IHS, it should not exceed the
corresponding specification given in the processor datasheet.
• When a compressive static load is necessary to ensure mechanical performance, it should not
exceed the corresponding specification given in the processor datasheet.
• The heatsink mass can also add additional dynamic compressive load to the package during a
mechanical shock event. Amplification factors due to the impact force during shock must be
taken into account in dynamic load calculations. The total combination of dynamic and static
compressive load should not exceed the processor datasheet compressive dynamic load
specification during a vertical shock. For example, with a 0.454 kg [1 lbm] heatsink, an
acceleration of 50G during an 11 ms trapezoidal shock with an amplification factor of 2 results
in approximately a 445 N [100 lbf] dynamic load on the processor package. If a 178 N [40 lbf]
static load is also applied on the heatsink for thermal performance of the TIM the processor
package could see up to a 623 N [140 lbf]. The calculation for the thermal solution of interest
should be compared to the processor datasheet specification.
No portion of the substrate should be used as a load-bearing surface.
Finally, the processor datasheet provides package handling guidelines in terms of maximum
recommended shear, tensile and torque loads for the processor IHS relative to a fixed substrate.
These recommendations should be followed in particular for heatsink removal operations.
2.1.2 Heatsink Attach
2.1.2.1 General Guidelines
There are no features on the LGA775 socket to directly attach a heatsink: a mechanism must be
designed to support the heatsink. In addition to holding the heatsink in place on top of the IHS, this
mechanism plays a significant role in the robustness of the system in which it is implemented, in
particular:
• Ensuring thermal performance of the TIM applied between the IHS and the heatsink. TIMs
based on phase change materials are very sensitive to applied pressure: the higher the pressure,
the better the initial performance. TIMs such as thermal greases are not as sensitive to applied
pressure. Designs should consider a possible decrease in applied pressure over time due to
potential structural relaxation in retention components.
10 Intel
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• Ensuring system electrical, thermal, and structural integrity under shock and vibration events.
The mechanical requirements of the heatsink attach mechanism depend on the weight of the
heatsink and the level of shock and vibration that the system must support. The overall
structural design of the motherboard and the system have to be considered when designing the
heatsink attach mechanism. Their design should provide a means for protecting LGA775
socket solder joints.
Note: Package pull-out during mechanical shock and vibration is constrained by the LGA775 socket load
plate (refer to the LGA775 Socket Mechanical Design Guide for further information).
2.1.2.2 Heatsink Clip Load Requirement
The attach mechanism for the heatsink developed to support the Celeron D processor in the
775-land LGA package should create a static load on the package between 18 lbf and 70 lbf
throughout the life of the product.
This load is required to ensure protect against fatigue failure of socket solder joint for a platform
seven year life.
2.1.2.3 Additional Guidelines
Processor Thermal/Mechanical Information
In addition to the general guidelines given above, the heatsink attach mechanism for the Celeron D
processor in the 775-land LGA package should be designed to the following guidelines:
• Holds the heatsink in place under mechanical shock and vibration events and applies force to
the heatsink base to maintain desired pressure on the thermal interface material. Note that the
load applied by the heatsink attach mechanism must comply with the package specifications
described in the processor datasheet. One of the key design parameters is the height of the top
surface of the processor IHS above the motherboard. The IHS height from the top of board is
expected to vary from 7.517 mm to 8.167 mm. This data is provided for information only, and
should be derived from:
— The height of the socket seating plane above the motherboard after reflow, given in the
LGA775 Socket Mechanical Design Guide with its tolerances.
— The height of the package, from the package seating plane to the top of the IHS, and
accounting for its nominal variation and tolerances that are given in the corresponding
processor datasheet.
• Engages easily, and if possible, without the use of special tools. In general, the heatsink is
assumed to be installed after the motherboard has been installed into the chassis.
• Minimizes contact with the motherboard surface during installation and actuation to avoid
scratching the motherboard.
2.2 Thermal Requirements
Refer to the processor datasheet for the processor thermal specifications. The majori ty of proces sor
power is dissipated through the IHS. There are no additional components (e.g., BSRAMs) that
generate heat in this package. The amount of power that can be dissipated as heat through the
processor package substrate and into the socket is usually minimal.
Intel® Celeron® D Processor in the 775-Land LGA Package Thermal Design Guide11
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Processor Thermal/Mechanical Information
Intel has introduced a new method for specifying the thermal limits for the Celeron D Processor in
the 775-Land LGA Package. The new parameters are the Thermal Profile and T
Thermal Profile defines the maximum case temper ature as a function of power being dissipated.
T
CONTROL
is a specification used in conjunction with the temperature reported by the on-die
thermal diode. Designing to these specifications allows optimization of thermal designs for
processor performance and acoustic noise reduction.
2.2.1 Processor Case Temperature and Power Dissipation
For the Celeron D processor in the 775-land LGA package, the case temperature is defined as the
temperature measured at the geometric center of the package on the surface of the IHS. For
illustration, Figure 2 shows the measurement location for a 37.5 mm x 37.5 mm [1.474 in x 1.474
in] FCLGA4 package with a 28.7 mm x 28.7 mm [1.13 in x 1.13 in] IHS top surface. Techniques
for measuring the case temperature are detailed in Section 3.4.
Figure 2. Processor Case Temperature Measurement Location
CONTROL
. The
37.5 mm
37.5 mm
2.2.2 Thermal Profile
The Thermal Profile defines the maximum case temperature as a function of processor power
dissipation. The TDP and Maximum Case Temperature are defined as the maximum values of the
thermal profile. By design the thermal solutions must meet the therma l profi le for all system
operating conditions and processor power levels.
37.5 mm
37.5 mm
Measure TCat this point
Measure TCat this point
(g eometric center of the package)
(g eometric center of the package)
The slope of the thermal profile was established assuming a generational improvement in th ermal
solution performance of about 10 % based on previous Intel reference design. This performance is
expressed as the slope on the thermal profile and can be thought of as the
thermal profile assumes a maximum ambient operating condition that is consistent with the
available chassis solutions.
12 Intel
Ψ
. The intercept on the
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T o determine compliance to the thermal profile, a measurement of the actual processor power
dissipated is required. The measured power is plotted on the Thermal Profile to determine the
maximum case temperature. Using the example in Figure 3, a power dissipation of 70 W has a case
temperature of 61 °C. Contact your Intel sales representative for assistance in processor power
measurement.
For the Intel Celeron D Processor in the 775-Land LGA Package, there are two thermal profiles to
consider. The Platform Requirement Bit (PRB) indicates which thermal profile is appropriate for a
specific processor. This document will focus on the development of thermal solutions to meet the
thermal profile for PRB=1. See the processor datasheet for the thermal profile and additional
discussion on the PRB.
Figure 3. Example Thermal Profile
75
70
65
60
Processor Thermal/Mechanical Information
Heatsink
Design Poin t
2.2.3 T
55
50
45
Case Temperature (C)
40
35
30
30 40 50 60 70 80 90 100 110
Watts
CONTROL
T
CONTROL
.
defines the maximum operating temperature for the on-die thermal diode when the
thermal solution fan speed is being controlled by the on-die thermal diode. The T
defines a very specific processor operating region where the T
is not specified. This parameter
C
Thermal Prof ile
FMB2
parameter
CONTROL
allows the system integrator a method to reduce the acoustic noise of the processor cooling
solution, while maintaining compliance to the processor thermal specification.
The value of T
CONTROL
processor idle power . As a result a processor with a high T
part with lower value of T
The value of T
CONTROL
is driven by a number of factors. One of the most significant of these is the
when running the same application.
CONTROL
CONTROL
is calculated such that regardless of the individual processor’s T
will dissipate more power than a
CONTROL
value the thermal solution should perform similarly. The higher leakage of some parts is offset by a
higher value of T
CONTROL
in such a way that they will behave virtually the same acoustically
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Processor Thermal/Mechanical Information
This is achieved in part by using the ΨCA vs. RPM and RPM vs. Acoustics (dBA) performance
curves from the Intel enabled thermal solution. A thermal solution designed to meet the thermal
profile should perform virtually the same for any value of T
Fan Speed Control” on page 29, for details on implementing a design using Tcontrol and the
Thermal Profile.
CONTROL
. See Section 4.3, “Acoustic
The value for T
CONTROL
is calculated by the system BIOS based on values read from a factory
configured processor register. Th e result can be used to program a fan speed control component.
See the processor datasheet for further details on reading the register and calculating T
2.3 Heatsink Design Considerations
To remove the heat from the processor, three basic parameters should be considered:
• The area of the surface on which the heat transfer takes place. Without any enhancements,
this is the surface of the processor package IHS. One method used to improve thermal
performance is by attaching a heatsink to the IHS. A heatsink increases the effective heat
transfer surface area by conducting heat out of the IHS and into the surrounding air through
fins attached to the heatsink base.
• The conduction path from the heat source to the heatsink fins. Providing a direct
conduction path from the heat source to the heatsink fins and selecting materials with higher
thermal conductivity typically improves heatsink performance. The length, thickness, and
conductivity of the conduction path from the heat source to the fins directly impact the thermal
performance of the heatsink. In particular, the quality of the contact between the package IHS
and the heatsink base has a higher impact on the overall thermal solution performance as
processor cooling requirements become stricter. Thermal interface material (TIM) is used to
fill in the gap between the IHS and the bottom surface of the heatsink, and thereby improve the
overall performance of the stack-up (IHS-TIM-Heatsink). With extremely poor heatsink
interface flatness or roughness, TIM may not adequately fill the gap. The TIM thermal
performance depends on its thermal conductivity as well as the pressure applied to it. Refer to
Section 2.3.4 and Appendix C for further information on TIM and on bond line management
between the IHS and the heatsink base.
• The heat transfer conditions on the surface on which heat transfer takes place.
Convective heat transfer occurs between the airflow and the surface exposed to the flow. It is
characterized by the local ambient temperature of the air, T
surface. The higher the air velocity over the surface and the cooler the air, the more ef ficient is
the resulting cooling. The nature of the airflow can also enhance heat transfer via convection.
Turbulent flow can provide improvement over laminar flow. In the case of a heatsink, the
surface exposed to the flow includes in particular the fin faces and the heatsink base.
CONTROL
, and the local air velocity over the
A
.
Active heatsinks typically incorporate a fan that helps manage the airflow through the heatsink.
Passive heatsink solutions require in-depth knowledge of the airflow in the chassis. Typically,
passive heatsinks see lower air speed. These heatsinks are therefore typically larger (and heavier)
than active heatsinks due to the increase in fin surface required to meet a required performance. As
the heatsink fin density (the number of fins in a given cross-section) increases, the resistance to the
airflow increases: it is more likely that the air travels around the heatsink instead of through it,
unless air bypass is carefully managed. Using air-ducting techniques to manage bypass area can be
an effective method for controlling airflow through the heatsink.
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2.3.1 Heatsink Size
The size of the heatsink is dictated by height restrictions for installation in a system and by the
space available on the motherboard and other considerations for component height and placement
in the area potentially impacted by the processor heatsink. The height of the heatsink must comply
with the requirements and recommendations published for the motherboard form factor of interest.
For the ATX/microATX form factor, it is recommended to use:
• The ATX motherboard keep-out footprint definition and heigh t restrictio ns for enabling
components, defined for the platforms designed with the LGA775 socket in Appendix F of this
design guide.
• The motherboard primary side height constraints defined in the ATX Specification V2.1 and
the microATX Motherboard Interface Specification V1.1 found at
http://www.formfactors.org/.
For the 1U and 2U server form factor, it is recommended to use:
• The 1U and 2U motherboard keep-out footprint definition and height restrictions for enabling
components, defined for the platforms designed with the LGA775 socket in Appendix E of
this design guide. Note that this keep-out footprint is similar to the ATX motherboard
keep-out, with minor differences in the areas surrounding the processor package.
• The 1U and 2U primary side constraints defined in the Thin Electronics Bay specification
found at http://www.ssiforum.org/.
Processor Thermal/Mechanical Information
The resulting space available above the motherboard is generally not entirely available for the
heatsink. The target height of the heatsink must take into account airflow considerations (for fan
performance for example) as well as other design considerations (air duct, etc.).
2.3.2 Heatsink Mass
With the need for pushing air cooling to better performance, heatsink solutions tend to grow larger
(increase in fin surface) resulting in increased weight. The insertion of highly thermally conductive
materials like copper to increase heatsink thermal conduction performance results in even heavier
solutions. As mentioned in Section 2.1, “Mechanical Requirements” on page 9, the heatsink weight
must take into consideration the package and socket load limits, the heatsink attach mechanical
capabilities, and the mechanical shock and vibration profile targets. Beyond a certain heatsink
weight, the cost of developing and implementing a heatsink attach mechanism that can ensure the
system integrity under the mechanical shock and vibration profile targets may become prohibitive.
The recommended maximum heatsink weight for the Celeron D processor in the 775-land LGA
package is 450g for the ATX form factor. This weight includes the fan and the heatsink only. The
attach mechanism (clip, fasteners, etc.) is not included.
The weight of the heatsinks for server form factors tends to be heavier than desktop form factors
and therefore there isn't a recommended maximum weight. These solutions are sometimes fastened
to the motherboard with the use of a backplate on the secondary side or in some cases are directly
mounted to the server chassis. In all cases, system integrators must ensure that the load
specifications for the package are met during shock and vibration testing.
2.3.3 Package IHS Flatness
The package IHS flatness for the product is specified in t he pr ocesso r datasheet and can be us ed as
a baseline to predict heatsink performance during the design phase.
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Processor Thermal/Mechanical Information
Intel recommends testing and validating heatsink performance in full mechanical enabling
configuration to capture any impact of IHS flatness change due to combined socket and heatsink
loading. While socket loading alone may increase the IHS warpage, the heatsink preload
redistributes the load on the package and improves the resulting IHS flatness in the enabled state.
2.3.4 Thermal Interface Material
Thermal interface material application between the processor IHS and the heatsink base is
generally required to improve thermal conduction from the IHS to the heatsink. Many th erm a l
interface materials can be pre-applied to the heatsink base prior to shipment from the heatsink
supplier and allow direct heatsink attach, without the need for a separate thermal interface material
dispense or attach process in the final assembly factory.
All thermal interface materials should be sized and positioned on the heatsink base in a way that
ensures the entire processor IHS area is covered. It is important to compensate for heatsink-toprocessor attach positional alignment when selecting the proper thermal interface material size.
When pre-applied material is used, it is recommended to have a protective cover over it. This cover
must be removed prior to heatsink installation.
2.3.5 Summary
In summary, considerations in heatsink design include:
• The local ambient temperature T
and the corresponding maximum T
performance parameter, Ψ
information on the definition and the use of Ψ
at the heatsink, the power being dissipated by the processor,
A
. These parameters are usually combined in a cooling
C
(case to air thermal characterization parameter). More
CA
is given in Section 2.4 below.
CA
• Heatsink interface (to IHS) surface characteristics, including flatness and roughness.
• The performance of the thermal interface material used between the heatsink and the IHS.
• The required heatsink clip static load, between 18 lbf to 70 lbf throughout the life of the
product (Refer to Section 2.1.2.2, “Heatsink Clip Load Requirement” on page 11 for further
information).
• Surface area of the heatsink.
• Heatsink material and technology.
• Volumetric airflow rate over the heatsink surface area.
• Development of airflow entering and within the heatsink area.
• Physical volumetric constraints placed by the system.
2.4 System Thermal Solution Considerations
2.4.1 Improving Chassis Thermal Performance
The heat generated by components within the chassis must be removed to provide an adequate
operating environment for both the processor and other system compo nents. Moving air through
the chassis brings in air from the external ambient environment and transports the heat generated
by the processor and other system components out of the system. The number, size and relative
position of fans and vents determine the chassis thermal performance, and the resulting ambient
temperature around the processor. The size and type (passive or active) of the thermal solution and
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Processor Thermal/Mechanical Information
the amount of system airflow can be traded off against each other to meet specific system design
constraints. Additional constraints are board layout, spacing, component placement, acoustic
requirements and structural considerations that limit the thermal solution size. For more
information, refer to the Performance ATX Desktop System Thermal Design Suggestions or
Performance microATX Desktop System Thermal Design Suggestions documents available on the
http://www.formfactors.org/ web site. For more information on 1U and 2U server refer to the Thin
Electronics Bay Specifications at http://www.ssiforum.org.
In addition to passive heatsinks, fan heatsinks and system fans, other solutions exist for cooling
integrated circuit devices. For example, ducted blowers, heat pipes and liquid cooling are all
capable of dissipating additional heat. Due to their varying attributes, each of these solutions may
be appropriate for a particular system implementation.
To develop a reliable, cost-effective thermal solution, thermal characterization and simulation
should be carried out at the entire system level, accounting for the thermal requirements of each
component. In addition, acoustic noise constraints may limit the size, number, placement, and types
of fans that can be used in a particular design.
To ease the burden on thermal solutions, the Thermal Monitor feature and associated logic have
been integrated into the silicon of the Celeron D Processor in the 775-land LGA package. By
taking advantage of the Thermal Monitor feature, system designers may reduce thermal solution
cost by designing to TDP instead of maximum power. Thermal Monitor attempts to protect the
processor in rare excursions of workload above TDP. Implementat ion op tions and
recommendations are described in Section 4.0, “Thermal Management Logic and Thermal
Monitor” on page 23 and Section 4.2.2, “Thermal Control Circuit” on page 24.
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Thermal Metrology
3.0 Thermal Metrology
This chapter discusses guidelines for testing thermal solutions, including measuring processor
temperatures. In all cases, the thermal engineer must measure power dissipation and temperature
to validate a thermal solution. To define the performance of a thermal solution the thermal
characterization parameter, Ψ (psi), will be used.
3.1 Characterizing Cooling Performance Requirements
The idea of a thermal characterization parameter, Ψ (psi), is a convenient way to characterize the
performance needed for the thermal solution and to compare thermal solutions in identical
situations (heat source, local ambient conditions). The thermal characterization parameter is
calculated using total package power. Note that heat transfer is a three-dimensional phenomenon
that can rarely be accurately and easily modeled by a single resistance parameter like Ψ.
The case-to-local ambient thermal characterization parameter value (
the thermal performance of the overall thermal solution that is attached to the processor package. It
is defined by the following equation, and measured in units of °C/W:
Equation 1.
Where:
Ψ
T
T
P
The case-to-local ambient thermal characterization parameter of the processor,
of
sink-to-local ambient thermal characterization parameter:
Equation 2.
Where:
Ψ
) is used as a measure of
CA
Ψ
= (TC - TA) / P
CA
= Case-to-local ambient thermal characterization parameter (°C/W)
CA
= Processor case temperature (°C)
C
= Local ambient temperature in chassis at processor (°C)
A
= Processor total power dissi pation (W) (assumes all power dissipates through the IHS)
D
Ψ
, the thermal interface material thermal characterization parameter, and of ΨSA, the
CS
Ψ
= ΨCS + Ψ
CA
SA
D
Ψ
, is composed
CA
Ψ
= Thermal characterization parameter of the thermal interface material (°C/W)
CS
Ψ
= Thermal characterization parameter from heatsink-to-local ambient (°C/W)
SA
Ψ
is strongly dependent on the thermal conductivity and thickness of the TIM between the
CS
heatsink and IHS.
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Ψ
is a measure of the thermal characterization parameter from the bottom of the heatsink to the
SA
local ambient air.
Ψ
is dependent on the heatsink material, thermal conductivity, and geometry. It
SA
is also strongly dependent on the air velocity through the fins of the heatsink.
Figure 4 illustrates the combination of the different thermal characterization parameters.
Figure 4. Processor Thermal Characterization Parameter Relationships
T
T
A
A
Heatsink
Heatsink
T
T
S
TIM
TIM
Processor
Processor
IHS
IHS
S
T
T
C
C
Thermal Metrology
Ψ
Ψ
CA
CA
LGA775 Socket
LGA775 Socket
3.1.1 Example
The cooling performance, Ψ
in the previous section:
• The case temperature T
datasheet.
• Define a target local ambient temperature at the processor, T
Since the processor thermal profile applies to all processor frequencies, it is important to identify
the worst case (lowest Ψ
strategy such that a given heatsink can cover a given range of processor frequencie s.
The following provides an illustration of how one might determine the appropriate performance
targets. The example power and temperature numbers used here are not related to any Intel
processor thermal specifications, and are for illustrative purposes only.
Assume the datasheet TDP is 100 W and the maximum case temperature from the thermal profile
for 100W is 67 °C. Assume as well that the system airflow has been designed such that the local
ambient temperature is 38 °C. Then the following could be calculated using Equation 1:
T o determine the required heatsink performance, a heatsink solution provider would need to
determine Ψ
heatsink solution were designed to work with a TIM material performing at Ψ
solving for Equation 2 from above, the performance of the heatsink would be:
System Board
System Board
is defined using the thermal characterization parameter described
CA,
and thermal design power TDP given in the processor
C-MAX
.
A
) for a targeted chassis (characterized by TA) to establish a design
CA
Ψ
= (TC – TA) / TDP = (67 – 38) / 100 = 0.29 °C/W
CA
performance for the selected TIM and mechanical load configuration. If the
CS
0.10 °C/W,
CS
Ψ
= ΨCA – ΨCS = 0.29 – 0.10 = 0.19 °C/W
SA
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Thermal Metrology
3.2 Processor Thermal Solution Performance Assessment
Thermal performance of a heatsink should be assessed using a thermal test vehicle (TTV) provided
by Intel. The TTV is a well-characterized thermal tool, whereas real processors can introduce
additional factors that can impact test results. In particular, the power level from actual processors
varies significantly, even when running the maximum power application provided by Intel, due to
variances in the manufacturing process. The TTV provides consistent power and power density for
thermal solution characterization and results can be easily translated to real processor performance.
Once the thermal solution is designed and validated with the TTV, it is strongly recommended to
verify functionality of the thermal solution on real processors and on fully integrated
systems.Contact your Intel field sales representative for further information on TTV or regarding
accurate measurement of the power dissipated by an actual processor.
3.3 Local Ambient Temperature Measurement Guidelines
The local ambient temperature TA (or TLA) is the temperature of the ambient air surrounding the
processor. For a pas sive heatsink, T
actively cooled heatsink, it is the temperature of inlet air to the active cooling fan.
It is worthwhile to determine the local ambient temperature in the chassis around the processor to
understand the effect it may have on the case temperature.
T
is best measured by averaging temperature measurements at multiple locations in the heatsink
A
inlet airflow. This method helps reduce error and eliminate minor spatial variations in temperature.
The following guidelines are meant to enable accurate determination of the localized air
temperature around the processor during system thermal testing.
is defined as the heatsink approach air temperature; for an
A
3.3.1 Measuring Active Heatsinks
• It is important to avoid taking measurement in the dead flow zone that usually develops above
the fan hub and hub spokes. Measurements should be taken at four different locations
uniformly placed at the center of the annulus formed by the fan hub and the fan housing to
evaluate the uniformity of the air temperature at the fan inlet. The thermocouples should be
placed approximately 3mm to 8 mm [0.1 to 0.3 in] above the fan hub vertically and halfway
between the fan hub and the fan housing horizontally as shown in Figure 5 (avoiding the hub
spokes).
• Using an open bench to characterize an active heatsink can be useful, and usually ensures
more uniform temperatures at the fan inlet. However, additional tests that include a solid
barrier above the test motherboard surface can help evaluate the potential impact of the
chassis. This barrier is typically clear Plexiglas*, extending at least 100 mm [4 in] in all
directions beyond the edge of the thermal solution. Typical distance from the motherboard to
the barrier is 81 mm [3.2 in].
• For even more realistic airflow, the motherboard should be populated with significant elements
like memory cards, graphic card, and chipset heatsink. If a barrier is used, the thermocouple
can be taped directly to the barrier with a clear tape at the horizontal location as previously
described, half way between the fan hub and the fan housing.
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Thermal Metrology
• If a variable speed fan is used, it may be useful to add a thermocouple taped to the barrier
above the location of the temperature sensor used by the fan to check its speed setting against
air temperature. When measuring T
other system components, it is likely that the T
non-uniform temperature distribution across the inlet fan section.
Note: Testing an active heatsink with a variable speed fan can be done in a thermal chamber to capture
the worst-case thermal environment scenarios. Otherwise, when doing a bench top test at room
temperature, the fan regulation prevents the heatsink from operating at its maximum capability. To
characterize the heatsink capability in the worst-case environment in these conditions, disable the
fan regulation and power the fan directly, based on guidance from the fan supplier.
in a chassis with a live motherboard, add-in cards, and
A
measurements will reveal a highly
A
Figure 5. Measuring T
— Active Heatsink
LA
NOTE: Dimensions in drawing not to scale.
3.3.2 Measuring Passive Heatsinks
•
Thermocouples should be placed approximately 13 to 25 mm [0.5 to 1.0 in.] away from
processor and heatsink as shown in Figure 6. The thermocouples should be placed
approximately 51 mm [2.0 in.] above the baseboard. The dimension above the baseboard will
vary depending on the maximum height in the intended form factor. This placement guideline
is meant to minimize the effect of localized hot spots from baseboard components.
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Thermal Metrology
Figure 6. Measuring T
NOTE: Dimensions in drawing not to scale.
— Passive Heatsink
LA
3.4 Processor Case Temperature Measurement Guidelines
To ensure functionality and reliability, the Celeron D Processor in the 775-land LGA package is
specified for proper operation when T
processor datasheet. The measurement location for T
shows the location for T
measurement.
C
Special care is required when measuring T
Thermocouples are often used to measure T
is maintained at or below the thermal profile as listed in the
C
to ensure an accurate temperature measurement.
C
. Before any temperature measurements are made, the
C
is the geometric center of the IHS. Figure 2
C
thermocouples must be calibrated, and the complete measurement system must be routinely
checked against known standards. When measuring the temperature of a surface that is at a
different temperature from the surrounding local ambient air, errors could be introduced in the
measurements. The measurement errors could be caused by poor thermal contact between the
thermocouple junction and the surface of the integrated heat spreader, heat loss by radiation,
convection, by conduction through thermocouple leads, or by contact between the thermocouple
cement and the heatsink base.
Appendix D defines a reference procedure for attaching a thermocouple to the IHS of an FC-LGA4
processor package for T
measurement. This procedure takes into account the specific features of
C
the FC-LGA4 package and of the LGA775 socket for which it is intended.
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Thermal Management Logic and Thermal Monitor
4.0 Thermal Management Logic and Thermal Monitor
4.1 Processor Power Dissipation
An increase in processor operating frequency not only increases system performance, but also
increases the processor power dissipation. The relationship between frequency and power is
generalized in the following equation:
P = CV2F
Where P = power, C = capacitance, V = voltage, F = frequency.
From this equation, it is evident that power increases linearly with frequency and with the square of
voltage. In the absence of power saving technologies, ever increasing frequencies will result in
processors with power dissipations in the hundreds of watts. Fortunately, there are numerous ways
to reduce the power consumption of a processor, and Intel is aggressively pursuing low power
design techniques. For example, decreasing the operating voltage, reducing unnecessary transistor
activity, and using more power efficient circuits can significantly reduce processor power
consumption.
An on-die thermal management feature called Thermal Monitor is available on the Celeron D
processor in the 775-land LGA package. It provides a thermal management approach to support the
continued increases in processor frequency and performance. By using a highly accurate on-die
temperature sensing circuit and a fast acting Thermal Control Circuit (TCC), the processor can
rapidly initiate thermal management control. The Thermal Monitor can reduce cooling solution
cost, by allowing thermal designs to target TDP.
4.2 Thermal Monitor Implementation
On the Celeron D processor in the 775-land LGA package, the Thermal Monitor is integrated into
the processor silicon. The Thermal Monitor includes:
• A bi-directional signal (PROCHOT#) that indicates if the processor has reached its maximum
temperature or can be asserted externally to activate the Thermal Control Circuit (TCC).
• A TCC that will attempt to reduce processor temperature by rapidly reducing power
consumption when the on-die temperature sensor indicates that it has reached the maximum
operating point.
• Registers to determine the processor thermal status.
4.2.1 PROCHOT# Signal
The Intel Celeron D processor in the 775-Land LGA Package implements a bi-directional
PROCHOT# capability to allow system designs to protect various components from
over-temperature situations. The PROCHOT# signal is bi-directional in that it can either signal
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Thermal Management Logic and Thermal Monitor
when the processor has reached its maximum operating temperature or be driven from an external
source to activate the TCC. The ability to activate the TCC via PROCHOT# can provide a means
for thermal protection of system components.
One application is the thermal protection of voltage regulators (VR). System designers can create a
circuit to monitor the VR temperature and activate the TCC when the temperature limit of the VR
is reached. By asserting PROCHOT# (pulled-low), which activates the TCC, the VR can cool
down as a result of reduced processor power consumption. Bi-directional PROCHOT# can allow
VR thermal designs to target maximum sustained current instead of maximum current. Systems
should still provide proper cooling for the VR and rely on bi-directional PROCHOT# only as a
backup in case of system cooling failure.
The PROCHOT# signal is available internally to the processor as well as externally. External
indication of the processor temperature status is provided through the bus signal PROCHOT#.
When the processor temperature reaches the trip point, PROCHOT# is asserted. When the
processor temperature is below the trip point, PROCHOT# is deasserted. Assertion of the
PROCHOT# signal is independent of any register settings within the processor. It is asserted any
time the processor die temperature reaches the trip point. The point where the TCC activates is set
to the same temperature at which PROCHOT# asserts.
4.2.2 Thermal Control Circuit
The TCC portion of the Thermal Monitor must be enabled for the processor to operate within
specifications. The Thermal Monitor’s TCC, when active, lowers the processor temperature by
reducing the power consumed by the processor. In the original implementation of thermal monitor
this is done by changing the duty cycle of the internal processor clocks, resulting in a lower
effective frequency. When active, the TCC turns the processor clocks off and then back on with a
predetermined duty cycle. The duty cycle is processor specific, and is fixed for a particular
processor. The maximum time period the clocks are disabled is ~3 μs, and is frequency dependent.
Higher frequency processors will disable the internal clocks for a shorter time period. Figure 7
illustrates the relationship between the internal processor clocks and PROCHOT#.
Performance counter registers, status bits in model specific registers (MSRs), and the PROCHOT#
output pin are available to monitor the Thermal Monitor behavior.
Figure 7. Concept for Clocks under Thermal Monitor Control
PROCHOT#
Normal clock
Internal clock
Duty cycle control
Resultant
internal clock
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4.2.3 Operation and Configuration
T o maintain compatibility with previous generations of processors, which have no integrated
thermal logic, the Thermal Control Circuit portion of Thermal Monitor is disabled by default.
During the boot process, the BIOS must enable the Thermal Control Circuit.
Note: Thermal Monitor must be enabled to ensure proper processor operation.
The Thermal Control Circuit feature can be configured and monitored in a number of ways. OEMs
are required to enable the Thermal Control Circuit while using various registers and outputs to
monitor the processor thermal status. The Thermal Control Circuit is enabled by the BIOS setting a
bit in an MSR (model specific register). Enabling the Thermal Control Circuit allows the processor
to attempt to maintain a safe operating temperature without the need for special software drivers or
interrupt handling routines. When the Thermal Control Circuit has been enabled, processor power
consumption will be reduced within a few hundred clock cycles after the thermal sensor detects a
high temperature, i.e. PROCHOT# assertion. The Thermal Control Circuit and PROCHOT#
transition to inactive once the temperature has been reduced below the thermal trip point, although
a small time-based hysteresis has been included to prevent multiple PROCHOT# transit ions
around the trip point. External hardware can monitor PROCHOT# and generate an interrupt
whenever there is a transition from active-to-inactive or inactive-to-active. PROCHOT# can also
be configured to generate an internal interrupt which would initiate an OEM supplied interrupt
service routine. Regardless of the configuration selected, PROCHOT# will always indicate the
thermal status of the processor.
Thermal Management Logic and Thermal Monitor
The power reduction mechanism of thermal monitor can also be activated manually using an
on-demand mode. Refer to Section 4.2.4 for details on this feature.
4.2.4 On-Demand Mode
For testing purposes, the thermal control circuit may also be activated by setting bits in the ACPI
MSRs. The MSRs may be set based on a particular system event (e.g., an interrupt generated after
a system event), or may be set at any time through the operating system or custom driver control
thus forcing the thermal control circuit on. This is referred to as “on-demand” mode. Activating the
thermal control circuit may be useful for thermal solution investigations or for perform ance
implication studies. When using the MSRs to activate the on-demand clock modulation feature, the
duty cycle is configurable in steps of 12.5%, from 12.5% to 87.5%.
For any duty cycle, the maximum time period the clocks are disabled is ~3 s. This time period is
frequency dependent, and decreases as frequency increases. To achieve different duty cycles, the
length of time that the clocks are disabled remains constant, and the time period that the clocks are
enabled is adjusted to achieve the desired ratio. For example, if the clock disable period is 3 µs, and
a duty cycle of 1/4 (25%) is selected, the clock-on time would be reduced to approx i mately 1 µs
[on time (1 µs) ÷ total cycle time (3 + 1) µs = 1/4 duty cycle]. Similarly, for a duty cycle of 7/8
(87.5%), the clock on time would be extended to 21 µs [21 ÷ (21 + 3) = 7/8 duty cycle].
In a high-temperature situation, if the thermal control circuit and ACPI MSRs (automatic and
on-demand modes) are used simultaneously, the fixed duty cycle determined by automatic mode
would take precedence.
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Thermal Management Logic and Thermal Monitor
4.2.5 System Considerations
Intel requires the Thermal Monitor and Thermal Control Circuit to be enabled for all Celeron D
processors in the 775-land LGA package based systems. The thermal control circuit is intended to
protect against short term thermal excursions that exceed the capability of a well designed
processor thermal solution. Thermal Monitor should not be relied upon to compensate for a thermal
solution that does not meet the thermal profile up to the thermal design power (TDP).
Each application program has its own unique power profile, although the profile has some
variability due to loop decisions, I/O activity and interrupts. In general, compute intensive
applications with a high cache hit rate dissipate more processor power than applications that are
I/O intensive or have low cache hit rates.
The processor thermal design power (TDP) is based on measurements of processor power
consumption while running various high power applications. This data is used to determine those
applications that are interesting from a power perspective. These applications are then evaluated in
a controlled thermal environment to determine their sensitivity to activation of the thermal control
circuit. This data is used to derive the TDP targets published in the processor datasheet.
A system designed to meet the thermal profile at TDP and T
processor datasheet or datasheet greatly reduces the probability of real applications causing the
thermal control circuit to activate under normal operating conditions. Systems that do not meet
these specifications could be subject to more frequent activation of the thermal control circuit
depending upon ambient air temperature and application power profile. Moreover, if a system is
significantly under designed, there is a risk that the Thermal Monitor feature will not be capable of
maintaining a safe operating temperature and the processor could shutdown and signal
THERMTRIP#.
For information regarding THERMTRIP#, refer to the processor datasheet and to Section 4.2.8.1,
“Cooling System Failure Warning” on page 28.
values published in the
C-MAX
4.2.6 Operating System and Application Software Considerations
The Thermal Monitor feature and its thermal control circuit work seamlessly with ACPI compliant
operating systems. The Thermal Monitor feature is transparent to application software since the
processor bus snooping, ACPI timer, and interrupts are active at all times.
4.2.7 On-Die Thermal Diode
There are two independent thermal sensing devices in the Celeron D Processor in the 775-land
LGA package. One is the on-die thermal diode and the other is in the temperature sensor used for
the Thermal Monitor (and Thermal Monitor 2) and for THERMTRIP#. The Thermal Monitor’s
temperature sensor and the on-die thermal diode are independent and physically isolated devices.
Circuit constraints and performance requirements prevent the Thermal Monitor’s temperature
sensor and the on-die thermal diode from being located at the same place on the silicon. The
temperature distribution across the die may result in significant temperature differences between
the on-die thermal diode and the Thermal Monitor’s temperature sensor. This temperature
variability across the die is highly dependent on the application being run. As a result, it is not
possible to predict the activation of the thermal control circuit by monitoring the on-die thermal
diode.
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System integrators should note that there is no defined correlation between the on-die thermal
diode and the processor case temperature. The temperature distribution across the die is affected by
the power being dissipated, type of activity the processor is performing e.g., integer or floating
point intensive and the leakage current. The dynamic and independent nature of these effects
makes it difficult to provide a meaningful correlation for the processor population.
System integrators planning to use the thermal diode for system or component level fan control to
optimize acoustics need to refer to Section 4.3, “Acoustic Fan Speed Control” on page 29.
4.2.7.1 Reading the On-Die Thermal Diode Interface
The on-die thermal diode is accessible from a pair of pins on the processor. The fan speed
controller remote thermal sense signals should be connected to these pins per the vendor’s
recommended layout guidelines.
Table 3. Thermal Diode Interface
Pin Name Pin Number Pin Description
THERMDA B3 Diode anode
THERMDC C4 Diode anode
4.2.7.2 Correction Factors for the On-Die Thermal Diode
A number of issues can affect the accuracy of the temperature reported by thermal diode sensors.
These include the diode ideality and the series resistance, which are characteristics of the processor
on-die thermal diode. The processor datasheet provides specifications for these parameters. The
trace layout recommendations between the thermal diode sensors and the processor socket should
be followed as listed in the vendor datasheets. Design characteristics and usage models of the
thermal diode sensors should be reviewed in the datasheets available from the manufacturers.
The choice of a remote diode sensor measurement component has a significant impact on the
accuracy of the reported on-die diode temperature. Component vendors offer components that have
stated accuracy of ± 3 °C to ± 1 °C. The improved accuracy generally comes from the number of
times a current is passed through the diode and the ratio of the currents. Consult the vendor
datasheet for details on their measurement process and stated accuracy.
The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by the diode
equation:
Equation 3.
IFW = IS * (E
Where IFW = forward bias current, I
the diode, k = Boltzmann Constant and T = absolute temperature (Kelvin).
Equation 4.
qVD/nkT
-1)
= saturation current, q = electronic charge, V = voltage across
S
This equation determines the ideality factor of an individual diode.
For the purpose of determining a correction factor to use with the thermal sensor, the ideality
equation can be simplified to the following:
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T
ERROR
= T
MEASURED
* (1 - N
ACTUAL
/ N
TRIM
)
Where T
= correction factor to add to the reported temperature, T
ERROR
reported by the thermal sensor (Kelvin), N
diode, N
= the assumed ideality used by the thermal sensor . For the range of temperature
TRIM
where the thermal diode is being measured, 30 - 80° C, this error term is nearly constant.
The value of N
thermal diode. N
The series resistance, R
is available from the datasheet of the device measuring the processor on die
TRIM
ACTUAL
can be assumed to be typical for this equation.
, is provided to allow for a more accurate measurement of the on-die
T
thermal diode temperature. R
resistance or board trace resistance between the socket and the external remote diode thermal
sensor. R
can be used by remote diode thermal sensors with automatic series resistance
T
cancellation to calibrate out this error term. Another application is that a temperature offset can be
manually calculated and programmed into an offset register in the remote diode thermal sensors as
exemplified by Equation 5:
Equation 5.
T
= (RT * (N – 1) * I
ERROR
Where T
= sensor temperature error, N = sensor current ratio, k = Boltzmann Constant, q =
ERROR
electronic charge.
4.2.8 THERMTRIP# Signal
In the event of a catastrophic cooling failure, the processor will automatically shut down when the
silicon temperature has reached its operating limit. At this point the system bus signal
THERMTRIP# goes active and power must be removed from the processor. THERMTRIP#
activation is independent of processor activity and does not generate any bus cycles. Refer to the
processor datasheet for more information about THERMTRIP#.
ACTUAL
, as defined, includes the processor pins but does not include socket
T
FWmin
= the ideality factor of the on-die thermal
) / (nk/q * IN ln N)
MEASURED
= temperature
The temperature where the THERMTRIP# signal goes active is individually calibrated during
manufacturing. The temperature where THERMTRIP# goes active is roughly parallel to the
thermal profile and greater than the PROCHOT# activation temperature. Once configured, the
temperature at which the THERMTRIP# signal is asserted is neither re-configurable nor accessible
to the system.
4.2.8.1 Cooling System Failure Warning
The PROCHOT# signal may be useful as an indication of cooling system failure. Messages could
be sent to the system administrator to warn of the cooling failure, while the thermal control circuit
would allow the system to continue functioning or allow a graceful system shutdown. If no thermal
management action is taken, the silicon temperature may exceed the operating limits, causing
THERMTRIP# to activate and shut down the processor. Regardless of the system design
requirements or thermal solution ability, the Thermal Monitor feature must still be enabled to
ensure proper processor operation.
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4.2.9 How On-Die Thermal Diode, T
CONTROL
Together
The Celeron D Processor in the 775-land LGA package thermal specification is comprised of two
parameters, T
CONTROL
and Thermal Profile. The first step is to ensure the thermal solution by design
meets the thermal profile. If the system design will incorporate variable speed fan control Intel
recommends monitoring the on-die thermal diode to implement acoustic fan speed control. The
value of on-die thermal diode temperature determines which specification must be met.
4.2.9.1 On-Die Thermal Diode Less than T
CONTROL
If the thermal solution can maintain the thermal diode temperature to less than T
not specified.
4.2.9.2 On-Die Thermal Diode Greater than T
If the on-die thermal diode temperature exceeds T
thermal profile for T
for that power dissipation.
C
CONTROL
4.3 Acoustic Fan Speed Control
For information on acoustic fan speed control see the Intel® Pentium® 4 Processor on 90 nm
Process in the 775-Land LGA Package Thermal Design Guidelines.
and Thermal Profile Work
CONTROL
CONTROL
, then the thermal solution must meet the
, then T
is
C
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Intel Enabled Thermal Solutions
5.0 Intel Enabled Thermal Solutions
5.1 Thermal Solution Requirements
The thermal performance required for the heatsink is determined by calculating the
case-to-ambient thermal characterization parameter, Ψ
Metrology” on page 18. This is a basic thermal engineering parameter that may be used to evaluate
and compare different thermal solutions in similar boundary conditions. For the Celeron D, an
example of how Ψ
Equation 6. Case-to-Ambient Thermal Characterization Parameter
=Ψ
CA
is calculated is shown in Equation 6.
CA
oo
max
−
CTCT
)()(
LAC
WTDP
)(
=
84
, as explained in Section 3.0, “Thermal
CA
−
W
CC
387.67
=
ooo
C
354.0
W
In this calculation, T
and TDP are taken from the thermal profile specification in the processor
C max
datasheet.
Note: In this calculation, the T
ambient temperature (T
and TDP are constant, while ΨCA will vary according to the local
C max
).
LA
Table 4 shows an example of required thermal characterization parameters for the thermal solution
at various T
s. This table uses the T
LA
and TDP from the processor datasheet. These numbers
C max
are subject to change, and in case of conflict, the specifications in the processor datasheet
supersede the T
and TDP specifications in this document.
C max
Table 4. Thermal Characterization Parameter at Various TLA Levels
Intel® Celeron® D Processor 341 Required ΨCA (°C/W) of Thermal Solution at TLA = (°C)
Frequency TDP T
2.93 GHz 84 W 67.7 °C 0.280 0.330 0.389 0.449
C MAX
44.2 40 35 30
Figure 8 further illustrates the required thermal characterization parameter for the Celeron D
Processor in the 775-land LGA package at various operating ambient temperatures. The thermal
solution design must have a Ψ
less than the values shown for the given local ambient
CA
temperature.
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Intel Enabled Thermal Solutions
Figure 8. Thermal Characterizat ion Parameters for Various Operating Conditions
5.2 ATX Form Factor
Intel is enabling the following active thermal solutions for the Celeron D Processor in the 775-land
LGA package for Embedded Applications in the ATX, similar, or larger form factors.
Table 5. Enabled Thermal Solutions
Heatsink Manufacturer Intel Part Number
Sanyo-Denki* C25697-001
Nidec* C25704-002
These solutions have been tested in environments with a T
thermal solution verification should be performed in the final intended use.
up to 38° C. However, system-level
LA
5.3 1U Form Factor
Thermal solution design for the 1U form factor is challenging. Due to limited volume for the
heatsink, mainly in the direction of heatsink height, and the available amount of airflow, system
designers may have to make trade-offs in the system boundary condition requirements (i.e.,
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Intel Enabled Thermal Solutions
maximum TLA, acoustic requirements, etc.) to meet the processor’s thermal requirements. The
entire thermal solution, from heatsink design, chassis configuration, and airflow source, must be
optimized for server systems to obtain the best performing solution.
Intel has worked with a third-party vend or to enable a heatsink design for the Celeron D Processor
in the 775-land LGA package for the 1U form factor. This design was optimized for the 1U form
factor within the available volume for the thermal solution. The motherboard component keep-ins
are shown in Figure 37, “1U/2U Motherboard Component Keep-In Definition, Primary Side” on
page 62 and Figure 38, “1U/2U Motherboard Component Keep-In Definition, Secondary Side” on
page 63.
This solution requires 100 percent of the airflow to be ducted through the heatsink fins to prevent
heatsink bypass. A copper base and copper fin heatsink are attached to the motherboard with the
use of a backplate. This solution is shown in Figure 9.
Figure 9. 1U Copper Heatsink
Based on preliminary testing, this heatsink has shown to have a performance (Ψ
with 18 CFM of airflow. This will allow a maximum T
Thermal Profile specification as described in the processor datasheet. This heatsink solution uses
the Honeywell* PCM45F as the Thermal Interface Material (TIM). The performance of the
heatsink could improve with more airflow, however the final intended thermal solution including,
heatsink, airflow source, TIM, and attach mechanism must be validated by system integrators.
Developers of thermal solutions for the Intel Celeron D Processor in the 775-Land LGA Package
must ensure that the solution meets the processor thermal specifications as stated in the processor
datasheet and follow the recommended motherboard component keep-out as shown in Figure 37
and Figure 38. This keep-out will ensure that the processor thermal solution will not interfere with
the voltage regulator components. In addition to this, a thermal solution design must meet the
maximum component heights as specified by the 1U Thin Electronics Bay Specifications located at
http://www.ssiforum.org
outlined in the specification.
32 Intel
) of 0.325 °C/W
of 40 °C and meet the processors
LA
CA
. Figure 10 illustrates the z-height constraints of the 1U form factor as
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Figure 10. 1U Thermal Solution Z-Height Constraints
5.4 2U Form Factor
Intel has developed a reference thermal solution design for the Celeron D processor in the 775-land
LGA package for the 2U form factor. This design was optimized for the 2U form factor within the
available volume for the thermal solution. The motherboard component keep-outs can be seen in
Figure 37, “1U/2U Motherboard Component Keep-In Definition, Primary Side” on page 62 and
Figure 38, “1U/2U Motherboard Component Keep-In Definition, Secondary Side” on page 63.
Intel Enabled Thermal Solutions
This solution requires 100% of the airflow to be ducted through the heatsink fins in order to
prevent heatsink bypass. It is a copper base and copper fin heatsink that is attached to the
motherboard with the use of a backplate. This solution is shown in Figure 11.
Figure 11. 2U Copper Heatsink
The performance of this thermal solution at multiple airflow rates is shown in Figure 12. The
performance test data shown in the chart was collected to ensure that the thermal solution is
performing within expectations. This data implies no statistical significance. The final intended
thermal solution including, heatsink, airflow source, TIM, and attach mechanism must be validated
by system integrators. This heatsink solution uses the Shin-Etsu* G751 as the TIM.
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Figure 12. Case-to-Ambient Thermal Characterization Parameter Ψ
(°C/W)
CA
Developers of thermal solutions for the Celeron D processor in the 775-land LGA package must
ensure that the solution meets the processor thermal specifications as stated in the processor
datasheet and follow the recommended motherboard component keep-out as shown in Figure 37
and Figure 38. This keep-out will ensure that the processor thermal solution will not interfere with
the voltage regulator components. In addition to this, a thermal solution design must meet the
maximum component heights as specified by the 2U Thin Electronics Bay Specifications located at
http://www.ssiforum.org. Figure 13 illustrates the Z-height constraints of the 2U form factor as
outlined in the specification.
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Figure 13. 2U Height Restrictions
5.5 Reference Thermal Mechanical Solution
For information regarding the Intel Thermal/Mechanical Reference Design thermal solution and
design criteria for the ATX form factor, refer to the Intel Pentium 4 Processor on 90nm Process in
the 775-Land LGA Package Thermal Design Guidelines.
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Conclusion
6.0 Conclusion
As the complexities of today’s microprocessors increase, power dissipation requirements become
more exacting. Care must be taken to ensure that the additional power is properly dissipated. Heat
can be dissipated using passive heatsinks, fans and/or active cooling devices. Incorporating ducted
airflow solutions into the system thermal design can yield additional margin.
The Intel Celeron D Processor in the 775-Land LGA Package integrates thermal management logic
onto the processor silicon. The Thermal Monitor feature attempts to control the processor
temperature in the event of a thermal excursion beyond the processor heatsink capability. If the die
temperature reaches the factory-calibrated temperature, the Thermal Monitor will take steps to
reduce power consumption, causing the processor to cool down. Thermal Monitor cannot
compensate for a thermal solution that does not meet the thermal profile and TDP. The use of the
on-die thermal diode in an active fan speed control solution can provide acoustic benefits and
maintain the processor thermal specification. Various registers and bus signals are available to
monitor and control the processor thermal status.
A thermal solution designed to the thermal profile at the thermal design power (TDP), as specified
in the processor datasheet, can adequately cool the processor to a level where activation of the
Thermal Monitor feature is either very rare or non-existent. Automatic thermal management must
be used as part of the total system thermal solution.
The size and type of the heatsink, as well as the output of the fan can be varied to balance size, cost,
and space constraints with acoustic noise. This document has presented the conditions and
requirements for designing a heatsink solution for a system based on a Celeron D processor in the
775-land LGA package. Properly designed solutions provide adequate cooling to main tain the
processor thermal specification. This is accomplished by providing a low local ambient
temperature and creating a minimal thermal resistance to that local ambient temperature. Fan
heatsinks or passive heatsinks with ducted airflow can be used to cool the processor if proper
package temperatures cannot be maintained otherwise. By maintaining the processor case
temperature at the values specified in the processor datasheet, a system designer can be confident
of proper functionality and reliability of these processors.
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LGA775 Socket Heatsink Loading
Appendix A LGA775 Socket Heatsink Loading
A.1 LGA775 Socket Heatsink Considerations
The heatsink clip load is traditionally used for:
• Mechanical performance in shock and vibration.
— Refer to the Intel Pentium 4 Processor on 90nm Process in the 775-Land LGA Package
Thermal Design Guide for information on the structural design strategy for the Intel
RCBFH-3 Reference Design heatsink.
• Thermal interface performance:
— Required preload depends on TIM.
— Preload can be low for thermal grease.
In addition to mechanical performance in shock and vibration and TIM performance, the LGA775
socket requires a minimum heatsink preload to protect against fatigue failure of socket solder
joints.
Solder ball tensile stress is originally created when, after inserting a processor into the socket, the
LGA775 socket load plate is actuated. In addition, solder joint shear stress is caused by coefficient
of thermal expansion (CTE) mismatch induced shear loading. The solder joint compressive axial
force (F
stress.
Overall, the heatsink required preload is the minimum preload needed to meet all of these
requirements: Mechanical shock and vibration and TIM performance and LGA775 socket
protection against fatigue failure.
) induced by the heatsink preload helps to reduce the combined joint tensile and shear
axial
A.2 Metric for Heatsink Preload for Designs
Non-Compliant with Intel Reference Design
A.2.1 Heatsink Preload Requirement Limitations
Heatsink preload by itself is not an appropriate metric for solder joint force across various
mechanical designs and does not take into account:
• Heatsink mounting hole span
• Heatsink clip/fastener assembly stiffness and creep
• Board stiffness and creep
• Board stiffness modified by fixtures like backing plate, chassis attach, etc.
Simulation shows that the solder joint force (F
measured along the socket diagonally. The matching of F
socket solder joint in temperature cycling is equivalent to matching a target MB deflection.
Therefore, the heatsink preload for the LGA775 socket solder joint protection against fatigue
failure can be defined as the load required to create a target board downward deflection throughout
the life of the product.
) is proportional to the board deflection
axial
required to protect the LGA775
axial
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This board deflection metric provides guidance for mechanical designs that differ from the
reference design for ATX/µATX form factor.
A.2.2 Board Deflection Metric Definition
Board deflection is measured along either diagonal (refer to Figure 14):
d = dmax – (d1 + d2)/2
d’ = dmax – (d’1 + d’2)/2
Configurations in which the deflection is measured are defined in Table 6.
T o measure board deflection, follow industry-standard procedures such as IPC for board deflection
measurement. Height gauges and possibly dial gauges may also be used.
Table 6. Board Deflection Configuration Definitions
Configuration
Parameter
d_ref Yes No Beginning of Life (BOL) deflection, no preload
d_BOL Yes Yes BOL deflection with preload
d_EOL Yes Yes End of Life (EOL) deflection
Processor + Socket
load plate
Figure 14. Board Deflection Definition
d1
d’2
Heatsink Parameter Name
d’1
d2
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A.2.3 Board Deflection Limits
Deflection limits for the ATX/µATX form factor are:
d_BOL - d_ref= 0.09 mm and d_EOL - d_ref = 0.15 mm
and
d’_BOL – d’_ref= 0.09 mm and d_EOL’ – d_ref’ = 0.15 mm
Note: The heatsink preload must remain within the static load limits defined in the processor datasheet at
all times.
Note: Board deflection should not exceed board manufacturer specifications.
A.2.4 Board Deflection Metric Implementation Example
This section is for illustration only and relies on the following assumptions:
• 72 mm x 72 mm hole pattern of the reference design
• Board stiffness = 900 lb/in at BOL, with degradation that simulates board creep over time.
— Though these values are representative, they may change with selected material and board
manufacturing process. Check with your board vendor.
• Clip stiffness assumed constant – No creep.
Using Figure 15, the heatsink preload at BOL is defined to comply with d_EOL – d_ref = 0.15 mm,
depending on clip stiffness assumption.
Note: The BOL and EOL preload and board deflection differ. This is a result of the creep phenomenon.
The example accounts for the creep expected to occur in the board. It assumes no creep to occur in
the clip. However, a small amount of creep is accounted for in the plastic fasteners. This situation is
somewhat similar to the Intel Reference Design.
The impact of the creep on the board deflection is a function of the clip stiffness:
• The relatively compliant clips store strain energy in the clip under the BOL preload condition
and tend to generate increasing amounts of board deflection as the board creeps under
exposure to time and temperature.
• In contrast, stiffer clips store very little strain energy and therefore do not generate substantial
additional board deflection through life.
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Note: Board and clip creep modify board deflection over time and depend on board stiffness, clip
stiffness, and selected materials.
Note: Designers must define the BOL board deflection that will lead to the correct EOL board deflection.
Figure 15. Example: Defining Heatsink Pr eload Meeting Board Deflection Limit
A.2.5 Additional Considerations
Intel recommends to design to {d_BOL - d_ref = 0.15mm} at BOL when EOL conditions are not
known or difficult to assess
The following information is given for illustration only. It is based on the reference keep-out,
assuming there is no fixture that changes board stiffness:
d_ref is expected to be 0.18 mm on average, and be as high as 0.22 mm.
As a result, the board should be able to deflect 0.37 mm minimum at BOL.
Additional deflection as high as 0.09 mm may be necessary to account for additional creep effects
impacting the board/clip/fastener assembly. As a result, designs could see as much as 0.50mm total
downward board deflection under the socket.
In addition to board deflection, other elements need to be considered to define the space needed for
the downward board total displacement under load, like the potential interference of through-hole
mount component pin tails of the board with a mechanical fixture on the back of the board.
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Note: The heatsink preload must remain below the maximum load limit of the package at all times. Refer
to processor datasheet.
Note: Board deflection should not exceed board manufacturer specifications.
A.2.5.1 Board Stiffening Considerations
To protect the LGA775 socket solder joint, designers need to drive their mechanical design to:
• Allow downward board deflection t o put the socket balls in a desirable force state to protect
against fatigue failure of socket solder joint (refer to Section A.2.1, Section A.2.2 and
Section A.2.3.)
• Prevent board upward bending during mechanical shock event.
• Define load paths that keep the dynamic load applied to the package within specifications
published in the processor datasheet.
Limiting board deflection may be appropriate in situations like:
• Board bending during shock.
• Board creep with high heatsink preload.
However, the load required to meet the board deflection recommendation (refer to Section A.2.3)
with a very stiff board may lead to heatsink preloads exceeding package maximum load
specification. For example, such a situation may occur when using a backing plate that is flush with
the board in the socket area, and prevents the board to bend underneath the socket.
A.3 Heatsink Selection Guidelines
Evaluate carefully heatsinks coming with board stiffening devices (like backing plates), and
conduct board deflection assessments based on the board deflection metric.
Solutions derived from the reference design comply with the reference heatsink preload; for
example:
• The Intel Celeron D Processor in the 775-Land LGA Package.
• The Intel RCBFH-3 Reference Design available from licensed suppliers.
Intel is also collaborating with vendors participating in its third party test house program to
evaluate third party solutions. Vendor information will be available and updated regularly after
product launch at http://developer.intel.com. After selecting the processor, go to the processor
technical information page, then select Support Component.
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Heatsink Clip Load Metrology
Appendix B Heatsink Clip Load Metrology
B.4 Overview
This section describes a procedure for measuring the load applied by the heatsink/clip/fastener
assembly to a processor package. This procedure is recommended to verify that the preload is
within the design target range for a design, and in different situations. For example:
• Heatsink preload for the LGA775 socket.
• Quantify preload degradation under bake conditions.
B.5 Test Preparation
B.5.6 Heatsink Preparation
Three load cells are assembled into the base of the heatsink under test in the area interfacing with
the processor Integrated Heat Spreader (IHS) using load cells equivalent to those listed in Section
B.5.8, “Typical Test Equipment” on page 44.
To install the load cells, machine a pocket in the heatsink base as shown in Figure 16 and
Figure 17. The load cells should be distributed evenly, as close as possible to the pocket walls.
Apply wax around the circumference of each load cell and the surface of the pocket around each
cell to maintain the load cells in place during the heatsink installation on the processor and board
(Refer to Figure 17).
The depth of the pocket depends on the height of the load cell used for the test. It is necessary that
the load cells protrude out of the heatsink base. However, this protrusion should be minimized as it
will create additional load by artificially raising the heatsink base. The measurement offset depends
on the whole assembly stiffness (i.e. board, clip, fastener, etc.). For example, the Intel RCBFH-3
Reference Heatsink Design clip and fastener assembly has a stiffness of around 380 N/mm [2180
lb/in]. In that case, a protrusion of 0.038 mm [0.0015”] will create an extra load of 15 N [3.3 lb].
Figure 16 shows an example using the Intel RCBFH-3 Reference Heatsink designed for the
Celeron D processor in the 775–land LGA package.
When optimizing the heatsink pocket depth, the variation of the load cell height should also be
taken into account to make sure that all load cells protrude equally from the heatsink base. It may
be useful to screen the load cells before installing to minimize variation.
B.5.7 Remarks: Alternate Heatsink Sample Preparation
Ensuring that the load cells have minimum protrusion out of the heatsink base is paramount to
meaningful results. An alternate method to make sure that the test setup measures loads
representative of the non-modified design is:
1. Machine the pocket in the heat sink base to a depth such that the tips of the load cells are just
flush with the heat sink base.
2. Machine back the heatsink base by approximately 0.25 mm [0.01”] so that the load cell tips
protrude beyond the base.
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Heatsink Clip Load Metrology
These steps should preserve the original stack height of the heatsink assembly without affecting the
stiffness of the heatsink significantly.
Figure 16. Load Cell Installation in Machined Heatsink Base Pocket – Bottom View
Heatsink Base Pocket
~ 29 mm [~1.15”]
Package IHS Outline
(Top Surface)
Load Cells
Figure 17. Load Cell Installation in Machined Heatsink Base Pocket – Side View
Wax to maintain load cell in position
during heatsink installation
Height of pocket ~
height of selected
load cell
Load cell protr usion
(Note: To be optimized depending on assembly stiffness)
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Heatsink Clip Load Metrology
Figure 18. Preload Test Configuration
B.5.8 Typical Test Equipment
Preload Fixture (copper
c or e wit h milled out poc k et)
Load Cells (3x)
For the heatsink clip load measurement, use test equipment equivalent to that listed in Table 7.
Table 7. Typical Test Equipment
Item Description Part Number
Load cell
Notes: 1, 5
Data Logger (or scanner)
Notes: 2, 3, 4
NOTES:
1. Select load range depending on expected load level. It is best to operate in the high end of the load cell
capability if possible. Check with your load cell vendor for further information.
2. Since the load cells are calibrated in terms of mV/V, a data logger or scanner is required to supply 5 VDC
excitation and read the mV response. An automated model will take the sensitivity calibration of the load cells
and convert the mV output into pounds.
3. With the test equipment listed above, it is possible to automate data recording and control with a 6101-PCI
card (GPIB) added to the scanner, allowing it to be connected to a PC running LabVIEW* or StrainSmart*
software.
4. IMPORTANT: In addition to just a zeroing of the force reading at no applied load, it is important to calibrate
the load cells against known loads. Load cells tend to drift. Contact your load cell vendor for calibration tools
and procedure information.
5. When measuring loads under thermal stress (bake for example), load cell thermal capability must be
checked and the test setup must integrate any hardware used along with the load cell. For example, the
Model 13 load cells are temperature compensated up to 71°C as long as the compensation package (spliced
into the load cell's wiring) is also placed in the temperature chamber. The load cells can handle up to 121°C
(operating), but their uncertainty increases according to 0.02% rdg/°F.
Honeywell*-Sensotec* Model 13 subminiature load cells,
compression only. Select a load range depending on
load level being tested.
www.sensotec.com
Vishay* Measurements Group Model 6100 scanner with
a 6010A strain card (one card required per channel).
AL322BL
Model 6100
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Heatsink Clip Load Metrology
B.6 Test Procedure Examples
The following sections give two examples of load measurement. However, these are not meant to
be used in mechanical shock and vibration testing.
Any mechanical device used along with the heatsink attach mechanism must be included in the test
setup (e.g., backplate, attach to chassis, etc.). Before any test, make sure that the load cell has been
calibrated against known loads, following load cell vendor’s instructions.
B.6.9 Time-Zero, Room Temperature Preload Measurement
1. Preassemble mechanical components on the board as needed before mounting the board on an
appropriate support fixture that replicates the board attach to a target chassis.
For example: A standard ATX board should sit on ATX-compliant standoffs. If the attach
mechanism includes fixtures on the back of the board, those must be included, as the goal of
the test is to measure the load provided by the actual heatsink mechanism.
2. Install the test vehicle in the socket.
3. Assemble the heatsink reworked with the load cells to the board as shown for the Intel
RCBFH-3 reference heatsink example in Figure 18 and actuate attach mechanism.
®
4. Collect continuous load cell data at 1 Hz for the duration of the test. A minimum time to allow
the load cell to settle is generally specified by the load vendors (often three minutes). The time
zero reading should be taken at the end of this settling time.
5. Record the preload measurement (total from all three load cells) at the target time and average
the values over 10 seconds around this target ti me as well, i .e. in the interval, for example over
[target time – 5 seconds; target time + 5 seconds].
B.6.10 Preload Degradation under Bake Conditions
This section describes an example of testing for potential clip load degradation under bake
conditions.
1. Preheat thermal chamber to target temperature (45 ºC or 85 ºC, for example).
2. Repeat time-zero, room temperature preload measurement.
3. Place unit into preheated thermal chamber for specified time.
4. Record continuous load cell data as follows:
— Sample rate = 0.1 Hz for first three hours.
— Sample rate = 0.01 Hz for the remainder of the bake test.
5. Remove assembly from thermal chamber and set into room temperature conditions.
6. Record continuous load cell data for next 30 minutes at sample rate of 1 Hz.
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Thermal Interface Management
Appendix C Thermal Interface Management
To optimize a heatsink design, it is important to understand the impact of factors related to the
interface between the processor and the heatsink base. Specifically, the bond line thickness,
interface material area and interface material thermal conductivity should be managed to realize
the most effective thermal solution.
C.7 Bond Line Management
Any gap between the processor integrated heat spreader (IHS) and the heatsink base degrades
thermal solution performance. The larger the gap between the two surfaces, the greater the thermal
resistance. The thickness of the gap is determined by the flatness and roughness of both the
heatsink base and the integrated heat spreader, plus the thickness of the thermal interface material
(for example thermal grease) used between these two surfaces and the clamping force applied by
the heatsink attach clip(s).
C.8 Interface Material Area
The size of the contact area between the processor and the heatsink base will impact the thermal
resistance. There is, however, a point of diminishing returns. Unrestrained incremental increases in
thermal interface material area do not translate to a measurable improvement in thermal
performance.
C.9 Interface Material Performance
Two factors impact the performance of the interface material between the processor and the
heatsink base:
• Thermal resistance of the material
• Wetting/filling characteristics of the material
Thermal resistance is a description of the ability of the thermal interface material to transfer heat
from one surface to another. The higher the thermal resistance, the less efficient the interface
material is at transferring heat. The thermal resistance of the interface material has a significant
impact on the thermal performance of the overall thermal solution. The higher the thermal
resistance, the larger the temperature drop is across the interface and the more efficient the thermal
solution (heatsink, fan) must be to achieve the desired cooling.
The wetting or filling characteristic of the thermal interface material is its ability, under the load
applied by the heatsink retention mechanism, to spread and fill the gap between the processor and
the heatsink. Since air is an extremely poor thermal conductor, the more completely the interface
material fills the gaps, the lower the temperature drops across the interface. In this case, thermal
interface material area also becomes significant; the larger the desired thermal interface material
area, the higher the force required to spread the thermal interface material.
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Case Temperature Reference Methodology
Appendix D Case Temperature Reference
Methodology
D.10 Objective and Scope
This appendix defines a reference procedure for attaching a thermocouple to the IHS of an
FC-LGA4 processor package for T
features of the FC-LGA4 package and of the LGA775 socket for which it is intended.
It describes the recommended equipment for the reference thermocouple installation, including
tools and adhesive part numbers.
D.11 Definitions
Definitions of common acronyms used in this appendix are given in the table below:
Table 8. Definitions
measurement. This procedure takes into account the specific
C
Term Definition
TTV Thermal Test Vehicle
IPA Isopropyl Alcohol
DMM Digital Multi Meter
IHS Integrated Heat Spreader
D.12 Supporting Test Equipment
T o apply the reference thermocouple attach proced ure, it is recommended to use the equipment (or
equivalent) given in the table below.
Table 9. Supporting Test Equipment (Sheet 1 of 2)
Item Description Part Number
Measurement and Output
Microscope Olympus* Light microscope or equivalent SZ-40
DMM Digital Multi Meter for resistance measurement Not Available
Test Fixture(s
Micromanipulator
(See Note below)
Loctite* 498 Adhesive Super glue w/thermal characteristics 49850
Adhesive Accelerator Loctite* 7452 for fast glue curing 18490
Kapton* Tape For holding thermocouple in place Not Available
Micromanipulator set from YOU* Ltd. or equivalent.
Mechanical 3D arm with needle (not included) to maintain TC
bead location during the attach process.
Miscellaneous Hardware
)
YOU-3
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Table 9. Supporting Test Equipment (Sheet 2 of 2)
Item Description Part Number
Thermocouple Omega *,40 gauge, “T” Type 5SRTC-TT-T-40-72
Ice Point Cell
Hot Point Cell
Omega*, stable 0 ºC temperature source for calibration and
offset
Omega*, temperature source to control and understand meter
slope gain
Calibration and Control
TRCIII
CL950-A-110
NOTE: Three axes set consists of (1 each U-31CF), (1 each UX-6-6), (1 each USM6) and (1 each UPN) More
information is available at: http://www.narishige.co.jp/you_ltd/english/products/set/you-set.htm#3
D.13 Thermal Calibration and Controls
It is recommended that full and routine calibration of temperature measurement system be
performed before attempting to perform temperature case measurement of TTVs and live products.
Intel recommends checking the meter probe set against known standards. This should be done at
0 °C (using ice bath or other stable temperature source) and at an elevated temperature, around
80 °C (using an appropriate temperature source).
Wire gauge and length also should be considered as some less expensive measurement systems are
heavily impacted by impedance. There are numerous resources available throughout the industry to
assist with implementation of proper controls for thermal measurements.
Note: It is recommended to follow company standard procedures and wear safety items like glasses for
cutting the IHS and gloves for chemical handling.
Note: Ask your Intel field sales representative if you need assist ance to groove and/or install a
thermocouple according to the reference process.
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D.14 IHS Groove
Cut a groove in the package IHS according to Figure 19.
Figure 19. FC-LGA4 Package Reference Groove Drawing
Case Temperature Reference Methodology
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Case Temperature Reference Methodology
The orientation of the groove relative to the package pin 1 indicator (gold triangle in one corner of
the package) is shown. Figure 20 for the FC-LGA4 package IHS.
Figure 20. IHS Reference Groove on the FC-LGA4 Package
Pin Indicator
IHS Groove
When the processor is installed in the LGA775 socket, the groove is perpendicular to the socket
load lever, and on the opposite side of the lever, as shown Figure 21.
Figure 21. IHS Groove Orientation Relative to the LGA775 Socket
Select a machine shop that is capable of holding drawing specified tolerances. IHS channel
geometry is critical for repeatable placement of the thermocouple bead, ensuring precise thermal
measurements. The specified dimensions minimize the impact of the groove on the IHS under the
socket load. A larger groove may cause the IHS to warp under the socket load such that it does not
represent the performance of an ungrooved IHS on production packages.
Inspect parts for compliance to specifications before accepting from machine shop.
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Case Temperature Reference Methodology
D.15 Thermocouple Attach Procedure
D.15.1 Thermocouple Conditioning and Preparation
1. Use a calibrated thermocouple as specified in Section D.12 and Section D.13.
2. Measure the thermocouple resistance by holding both wires on one probe and the tip of th e
thermocouple to the other probe of the DMM. The measurement should be about~75 ohms for
40-gauge type T thermocouple.
3. Straighten the wire for about 38 mm [1½ inch] from the bead to place it inside the channel.
4. Bend the tip of the thermocouple at approximately 45 degree angle by about 0.8 mm [.030
inch] from the tip (Figure 22).
Figure 22. Bending the Tip of the Thermocouple
D.15.2 Thermocouple Attachment to the IHS
5. Clean groove with IPA and a lint free cloth removing all residues prior to thermocouple
attachment.
6. Place the thermocouple wire inside the groove; letting the exposed wire and bead extend about
3.2 mm [.125 inch] past the end of groove. Secure it with Kapton* tape (Figure 23).
Figure 23. Securing Thermocouple Wires with Kapton* Tape Prior to Attach
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Case Temperature Reference Methodology
7. Lift the wire at the middle of groove with tweezers and bend the front of wire to place the
thermocouple in the channel ensuring the tip is in contact with the end of the channel grooved
in the IHS (Figure 24 and Figure 25).
Figure 24. Thermocouple Bead Placement (View 1)
Figure 25. Thermocouple Bead Placement (View 2)
8. Place the TTV under the microscope unit (similar to the one used in Figure 29) to continue
with process. It is also recommended to use a fixture (like processor tray or a plate) to help
holding the unit in place for the rest of the attach process.
9. Press the wire down about 6mm [0.125"] from the thermocouple bead using the tweezers.
Look in the microscope to perform this task. Place a piece of Kapton* tape to hold the wire
inside the groove (Figure 26). Refer to Figure 27 for detailed bead placement.
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Figure 26. Position Bead on Groove Step
Kapton* tape
Figure 27. Detailed Thermocouple Bead Placement
Case Temperature Reference Methodology
Wire section into
the groove to
prepare for final
bead placement
10. Using the micromanipulator, install the needle near to the end of groove on top of
thermocouple. Using the X, Y & Z axes on the arm place the tip of needle on top of the
thermocouple bead. Press down until the bead is seated at the end of groove on top of the step
(see Figure 27 and Figure 28).
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Case Temperature Reference Methodology
Figure 28. Using 3D Micromanipulator to Secure Bead Location
11. Measure resistance from thermocouple end wires (hold both wires to a DMM probe) to the
IHS surface. This should be the same value as measured during the thermocouple conditioning
step (Figure 29).
Figure 29. Measuring Resistance between Thermocouple and IHS
12. Place a small amount of Loctite* 498 adhesive in the groove where the bead is installed. Using
a fine point device, spread the adhesive in the groove around the needle, the thermocouple
bead and the thermocouple wires already installed in the groove during Step 5 above. Be
careful not to move the thermocouple bead during this step (Figure 30).
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Case Temperature Reference Methodology
Figure 30. Applying the Adhesive on the Thermocouple Bead
13. Measure the resistance from the thermocouple end wires again using the DMM to ensure the
bead is still properly contacting the IHS.
D.15.3 Curing Process
1. Let the thermocouple attach set in the open-air for at least half an hour. It is not recommended
to use any curing accelerator for this step, as rapid contraction of the adhesive during curing
may weaken bead attach on the IHS.
2. Reconfirm electrical connectivity with DMM before removing the micromanipulator.
3. Remove the 3D Arm needle by holding down the TTV unit and lifting the arm.
4. Remove the Kapton* tape, straighten the wire in the groove so it lays flat all the way to the end
of the groove (Figure 31).
Figure 31. Thermocouple Wire Management in the Groove
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Case Temperature Reference Methodology
5. Using a blade to shave excess adhesive above the IHS surface (Figure 32).
Note: Take usual precautions when using open blades.
Figure 32. Removing Excess Adhesive from IHS
6. Install new Kapton* tape to hold the thermocouple wire down and fill the rest of groove with
adhesive (See Figure 33). Make sure the wire and insulation is entirely within the groove and
below the IHS surface.
Figure 33. Filling the Groove with Adhesive
Filling with
Adhesive
Kapton* Tape
7. Curing time for the rest of the adhesive in the groove can be reduced using Loctite*
Accelerator 7452.
8. Repeat Step 5 to remove any access adhesive to ensure flat IHS for proper mechanical contact
to the heatsink surface.
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Board Level PWM and Fan Speed Control Requirements
Appendix E Board Level PWM and Fan Speed
Control Requirements
To utilize all of the features in the Intel reference heatsink design or the Intel boxed processor
design, system integrators should verify the following functionality is present in the board design.
Please refer to the Fan Specification for 4-Wire PWM Controlled Fans.
Requirements Classification:
• Required – an essential part of the design necessary to meet specifications. Should be
considered a pass or fail in selection of a board.
• Recommended – necessary for consistency among designs. May be specified or expanded by
the system integrator.
The motherboard needs to have a fan speed control component that has the following
characteristics
• PWM output of 21-28 KHz (required).
• PWM output set to 25 KHz (recommended) this value is the design target for the reference and
for the Intel boxed processor solutions.
• Has external/remote thermal diode measurement capability (required).
• External/remote thermal diode sampling rate = 4 times per second (required).
• External/remote diode measurement is calibrated by the component vendor to account for the
diode ideality and package series resistance as listed in the appropriate datasheet.
(recommended).
Note: If the fan speed controller is not calibrated with the diode ideality and package series resistance,
verify the board manufacturer has made provisions within the BIOS setup or other utility to input
the corrections factors.
The BIOS must be enabled to program the following data into the fan speed controller.
• Turns on PWM functionality within the required frequency range (required).
• Has the minimum and maximum values for the fan speed (RPM) ramp (required).
• Has minimum temperature where the fan speed will begin ramping. (required).
• Has maximum temperature used for the fan speed (RPM) ramp set equal to T
(required).
Note: The fan speed component vendors provide libraries that are used by the BIOS writer to program the
component registers with the parameters listed above. Consult the appropriate vendor datasheet for
detailed information on programming their component.
CONTROL
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Mechanical Drawings
Appendix F Mechanical Drawings
The following table lists the mechanical drawings included in this appendix. These drawings refer
to the reference thermal mechanical enabling components for the Intel Celeron D Processor in the
775-Land LGA Package.
Note: Intel reserves the right to make changes and modifications to the design as necessary.
Table 10. Mechanical Drawings
Drawing Description Page
ATX/µATX Motherboard Keep-Out Footprint Definition and Height
Restrictions for Enabling Components, Sheet 1
ATX/µATX Motherboard Keep-Out Footprint Definition and Height
Restrictions for Enabling Components, Sheet 2
ATX/µATX Motherboard Keep-Out Footprint Definition and Height
Restrictions for Enabling Components, Sheet 3
1U/2U Motherboard Component Keep-In Definition, Primary Side 62
1U/2U Motherboard Component Keep-In Definition, Secondary Side 63
59
60
61
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Mechanical Drawings
Figure 34. ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 1
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Mechanical Drawings
Figure 35. ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 2
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Mechanical Drawings
Figure 36. ATX/µATX Motherboard Keep-Out Footprint Definition and Height Restrictions
for Enabling Components, Sheet 3
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Mechanical Drawings
Figure 37. 1U/2U Motherboard Component Keep-In Definition, Primary Side
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Mechanical Drawings
Figure 38. 1U/2U Motherboard Component Keep-In Definition, Secondary Side
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Vendor Information
Appendix G Vendor Information
This appendix includes supplier information for Intel enabled vendors for the Intel Celeron D
Processor in the 775-Land LGA Package thermal solutions.
Table 11 lists suppliers that produce Intel enabled reference components. The part numbers listed
below identifies these reference components. End-users are responsible for the verification of the
Intel enabled component offerings with the supplier. OEMs and System Integrators are responsible
for thermal, mechanical, and environmental validation of these solutions.
Table 11. Intel Reference Component Thermal Solution Provider
Supplier Part Description
Sanyo-Denki*
Nidec America
Corporation*
AVC*
(ASIA Vital
Components
Co., Ltd.*)
CoolerMaster* 2U reference solution
Active fan heatsink for
the Intel Celeron D
Processor in the
775-Land LGA Package
1U heatsink C69175 David Chao
Part
Number
C25697
C25704 Karl Mattson 360-666-2445 Karl.mattson@nidec.com
PSC-2U001
Contact Phone Email
Haruhiko (Harry)
Kawasumi
Wendy Lin (908) 252-9400 wendy@coolermaster.com
310-783-5430 haruhiko@sanyo-denki.com
+886-2-22996930
Ext: 619
david_chao@avc.com.tw
Note: These vendors and devices are listed by Intel as a convenience to Intel's general customer base, but
Intel does not make any representations or warranties whatsoev er regarding quality, reliability,
functionality, or compatibility of these devices. This list and/or these devices may be subject to
change without notice.
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