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June 1998
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Compaq Computer
Corporation
ECG Technology
Communications
ONTENTS
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Introducti on
Three PCI Hot Plug
Capabilities
Synergistic HighAvailability Techniques
PCI Hot Plug: Compaq
Strategy
Progress Towar d an
Industry Standard
Summary of PCI Hot
Plug
System Hardware
System Soft ware
Hardware and Software
Control
Adapters and Device
Drivers
Compatibility I ssues
Conclusion
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ECG080/0698
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ECHNOLOGY
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PCI Hot Plug Technology
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As an increasing number of companies migrate their business-critical applications to
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industry-standard servers, the need for high-availability solutions to minimize system
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downtime is increasing. Compaq, the world’s leading server provider, has historically
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taken a leadership role in developi ng i ndust ry-s tandar d t echnologi es. With the
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development of PCI Hot Plug technology, Compaq strengthens i t s r ole in provi ding hi gh-
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availability solutions for the enterprise.
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This technology brief summarizes the PCI Hot Plug technology and describes Compaq’s
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strategy for developing and standardi zi ng th is technol ogy.
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Please direct comments regarding this communication to the ECG Technology Communications Group at this Internet address:
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TechCom@compaq.com
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B
RIEF
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ECG080/0698
ECHNOLOGY BRIEF
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OTICE
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The information in this publication is subject to change without notice and is provided “AS IS”
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WITHOUT WARRANTY OF ANY KIND. THE ENTIRE RISK ARISING OUT OF THE USE
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OF THIS INFORMATION REMAINS WITH RECIPIENT. IN NO EVENT SHALL COMPAQ
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BE LIABLE FOR ANY DIRECT, CONSEQUENTI AL, INC I DE NT AL, SPECIAL, PUNITIVE
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OR OTHER DAMAGES WHATSOEVER (INCLUDING WITHOUT LIMITATION,
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DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS INTERRUPTION OR LOSS OF
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BUSINESS INFORMATION), EVEN I F COMPAQ HAS BEEN ADVI SE D OF T HE
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POSSIBILITY OF SUCH DAMAGES.
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The limited warranties for Compaq products are exclusively set forth in the documentation
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accompanying such products. Nothing herein should be construed as constituting a further or
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additional warranty.
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This publication does not constitute an endorsement of the product or products that were tested.
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The configuration or configurations tested or described may or may not be the only available
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solution. This test is not a determination of product quality or correctness, nor does it ensure
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compliance with any federal state or local requirements.
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Compaq, Contura, Deskpro, Fastar t , Compaq In sight Manager, LTE, PageMar q, Systempro,
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Systempro/LT, ProLiant, TwinTray, ROMPaq, LicensePaq, QVision, SLT, ProLinea, SmartStart,
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NetFlex, DirectPlus, QuickFind, RemotePaq, BackPaq, TechPaq, SpeedPaq, QuickBack, PaqFax,
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Presario, SilentCool, CompaqCare (design), Aero, SmartStation, MiniStation, and PaqRap,
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ProSignia, Concerto, Vocalyst, and MediaPilot are registered with the United States Patent and
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Tradema rk Office.
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Change is Good, Compaq Capital, Colinq, Armada, SmartQ, Counselor, CarePaq, Netelligent,
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Smart Uplink , Ext ended Repeater A rchitectu re, Scalabl e C lock Archit ecture, QuickChoi ce,
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Systempro/XL, Net1, LTE Elite, PageMate, SoftPaq, FirstPaq, SolutionPaq, EasyPoint, EZ Help,
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MaxLight, MultiLock, QuickBlank, QuickLock, UltraView, Innovate logo, and Compaq PC Card
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Solution logo are trademarks and/or service marks of Compaq Computer Corporation.
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Micr osoft, Windows, Windows NT, Windows NT Advanced Ser ver, SQL Server for Win d ows NT
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are trademarks and/or registered trademarks of Microsoft Corporation.
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NetWare and Novell are registered tra demarks and Intran etWar e, NDS, and Novel l Dir ectory
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Services are t rademar k s of Novell, Inc.
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Pentium is a registered trademark of Intel Corporation.
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Other product names mentioned herein may be trademarks and/or registered trademarks of their
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respective companies.
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©1998 Compaq Computer Corporation. All ri ghts reserved. Printed in the U.S.A.
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PCI Hot Plug Techno logy
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Fourth Edition (June 1998)
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ECG080/0698
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(cont.)
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ECG080/0698
ECHNOLOGY BRIEF
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NTRODUCTION
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Customers today need high-availability solutions that minimize or eliminate downtime. PCI Hot
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Plug technology allows a PCI adapter to be added, upgraded, or replaced while the host system is
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running and while other adapters in the system provide uninterrupted service. PCI Hot Plug
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technology adds to other high-availability solutions presently available from Compaq such as
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Recovery Server Options, Redundant Netelligent Network Interface Controllers (NICs), hot-
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pluggable power supplies, hot-pluggable fans, and hot-pluggable SCSI drives.
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Three PCI Hot Plug Capabilities
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PCI Hot Plug technology provides for three major capabilities: hot replacement, hot upgrade, and
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hot expansion.
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Hot replacement
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identical
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Hot upgrade
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replacing th e adapt er ’s device driver with an upgra ded device driver while the server is operating.
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Hot expansion
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while the server is operating.
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Synergistic High-Availability Techniques
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PCI Hot Plug technology represents a significant advance in fault-tolerant systems. To provide
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even greater benefit, PCI Hot Plug technology can be combined with redundant controller
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configurations, such as Compaq Redundant Netelligent NIC technology.
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Compaq Redundant Netelligent NIC technology allows two similar NICs to share a single
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ins tan ce of devi ce d river code. One NIC becomes the a ctive n etwork control ler, and the other
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NIC acts as a standby controller. If the active NIC fails, the network traffic can be switched
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automatically to the standby NIC. With PCI Hot Plug, the failed NIC can be replaced without
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shutting down the system. Thus, the end user can have continuous service and the administrator
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can eliminate both planned and unplanned downtime.
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PCI H
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Compaq’s decision to develop PCI Hot Plug technology is focused on addressing a key customer
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issue: as computing environments grow more complex, the business costs of unplanned system
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downtime are soaring. The increasing cost of unplanned downtime in business-critical
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environments, compounded by the time spent tracking the source of network or component
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failures, is creating a greater need for high-availability solutions like PCI Hot Plug.
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In the past, reliable and powerful around-the-clock performance was available only from
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expensive, proprietary systems. Although these proprietary solutions may give the developer an
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initial competitive advantage, they generally have not been well received by customers .
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Proprietary solutions tend to be more costly and less accessible. They also require the customer to
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be wary of compatibility issues.
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An open, industry-standard approach, such as Compaq’s PCI Hot Plug effort, has multiple
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benefits. First, customers benefit from the increased availability of the hot-plug solution.
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Because PCI Hot Plug is an open, industry standard, it allows multiple system providers,
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operating system (OS) developers, and adapter suppliers to implement PCI Hot Plug solutions.
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Additionally, customers have investment protection because hot plug is compatible with previous
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PCI st andards . Th erefore, an y new hot-plug system hardware, OSs, or ad apter device drivers are
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PCI compliant and will work with existing PCI-compliant systems. The entire system does not
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adapter into the same slot while the server is operating.
is the process of replacing an existing adapter with an
is the process of installing an
OT PLUG
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is the process of removing a failed or failing PCI adapter and inserting an
adapter or
additional
OMPAQ STRATEGY
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upgraded
adapter into a previously empty slot
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ECG080/0698
ECHNOLOGY BRIEF
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need t o be over hauled just because cer tain compon ents are hot-plug capable. The t echnol og y is
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fully backward compatible.
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Thes e same fact ors are als o benefits wh en viewed fr om an i ndus try pers p ective. For example, as
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an industry-wide standard, PCI Hot Plug technology is functional with multiple OSs, hardware
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systems, and adapters. This interoperability gives the industry a strong footing to ensure adoption
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of the t echnol og y and progress to other adva ncements. Beca u s e of t he focused effort on a s ingle
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standard, resources are not fragmented into modifying solutions for particular proprietary
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hardware or software but provide synergistic growth into more advanced technologies. As an
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open standard, PCI Hot Plug is attractive to the major OS and independent hardware vendors
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(IHVs) and encourages their development of compliant products.
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An open, industry standard clearly benefits Compaq as well. By developing PCI Hot Plug
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technology and initiating the industry standard for hot plug, Compaq extends its technology
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leadership position in the industry. Compaq will also benefit from the interoperability of the open
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standard, as it will provide a natural progression into further high-availability advancements.
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With the ProLiant 6500 a nd ProLiant 7000 servers, Compaq delivered the first industry-standard
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PCI Hot Plug systems and once again set the standard in high-availability and fault-tolerant
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solutions for the distributed enterprise.
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ROGRESS TOWARD AN INDUSTRY STANDARD
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Since Compaq’s June 1996 announcement to deliver PCI Hot Plug technology as an open,
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industry standar d, Compaq h a s worked with key hardware and software partners and t he industry-
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wide PCI standards committee. This effort allows customers to move forward in implementing
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this technology with greater flexibility. Compaq has taken several steps to ensure broad industry
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acceptance of the technolog y, i nclu d ing:
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Standardized PCI Hot Plug technology by initiating and chairing the PCI Special Interest
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Group (SIG) Hot Plug Workgroup. The workgroup included other industry leaders such as
Adaptec, Inc.; Cirrus Logic, Inc.; Digital Equipment Corporation; Hewlett-Packard
Company; IBM Corporation; Intel; Microsoft; Novell; Pro-Log Corporation; The Santa Cruz
Operation, Inc. (SCO); and Texas Instrument s In corporated. Efforts of the workgroup
allowed a quick release of the PCI Hot Plug Specification—only 14 months from the group’s
charter. For more information on the PCI Hot Plug Specification, visit the PCI SIG website
at http://www.pcisig.com.
Partnered with OS developers to ensure incorporation of the PCI Hot Plug standard in
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product releases. Compaq has taken a proactive role in ensuring broad OS support for hotplug capabilities. Actions to date range from the development of cross-company design
teams to the delivery of PCI Hot Plug platforms for testing OSs. Currently, Microsoft,
Novell, and SCO support PCI Hot Plug.
Worked with leading adapter vendors such as 3Com Corporation; Adaptec; Dialogic
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Corporation; Digi International; Mylex Corporation; QLogic Corporation; American
Megatrends, Inc. (AMI); Madge Networks; SMC Networks Inc.; and SysKonnect to ensure
broad accepta nce and r apid impl ement ation of the stan d ard .
Licensed PCI Hot Plug technology to be available in Intel architecture-based server platforms.
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Intel will incorporate Compaq’s implementation of PCI Hot Plug, including the hot-plug
controller and related system technologies, in future products.
Developed hot-plug aware drivers for Compaq NetFlex controllers, Netelligent controllers,
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Smart array controllers, and Fast-Wide SCSI-2 controllers.
(cont.)
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Developed the Compaq ProLiant 6500 and ProLiant 7000, a nnounced in August 1997, as th e
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first available server platforms conforming to the PCI Hot Plug Specification and added nextgeneration PCI Hot Plug features to Pentium II Xeon Models of the ProLiant 7000 announced
in June 1998.
Compaq is in a unique position to lead this standardization effort. Not only is Compaq a pioneer
in the development of systems hardware, but Compaq also has extensive experience in systems
configuration software and device driver development. Because of its unique position, Compaq
has been able to gather the support of major software developers and IHVs to deliver PCI Hot
Plug technology as an open, industry standard.
UMMARY OF
S
Taking a very general approach, a fully capable hot-plug system includes the hot-plug system
hardware, h ot-plug awar e software and OS support, hot-plug capable device drivers, and a hotplug aware user interface, as shown in Figure 1. The hardware an d software work together to
ensure that any hot-plug activity occurring on the PCI bus is benign to other devices on the PCI
bus.
System Hardwa re
It is important to note that while the PCI Hot Plug Specification identifies the technical
requirements of a hot-plug capable system, it does not specify the implementation of this
technology. In the specific implementation that Compaq developed, the PCI Hot Plug hardware
isolat es a single PCI slot from a ll other de vices on the PC I bus. Com paq’s PCI Hot Plug s ystem
hardware performs two main functions:
Powers down a single adapter slot, allowing insertion and removal of adapters
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Protects the system and other adapters from the electrica l effects of hot- plug operat ions
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(cont.)
PCI H
User Inte r fa ce
Software and OS Support Device Drivers
OT PLUG
PCI A dapter
Board
System
Hot-Plug Hardware
Figure 1: Generic PCI Hot Plug Technology
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Hot-Plug Controller and Slot-Specific Power Control
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The hot-p lug electronics designed by Compaq consist of t wo separa te elements: the hot-plug
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controller and the slot-specific power control. Compaq designed its hot-plug controller to manage
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the following components:
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PCI Bus.
isolate a single PCI slot from the rest of the system. Slot isolation permits insertion or
removal of an adapter without interruption to the server or other active adapters.
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Power.
PCI slot. To perform this function, the controller uses the slot-specific power control. The
slot-s p ecific power- contr ol electroni cs allow the proper power sequencin g on the PCI bus and
guarantee safe control of the power to the individual PCI adapters.
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Slot LED Indica tors.
implementation of hot-plug hardware, each slot has a green and an amber LED to indicate
slot status. The green LED indicates power to the slot and flashes while performing a power
state change; the amber LED indicates that the slot requires attention.
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PCI Hot Plug Button.
servers. The button is pressed to signal the software to initiate a power state change. While
the button is more convenient, the same functionality is provided through the software
interface. Each slot has its own button to indicate which slot is to be addressed by the
supporting software.
System Chassis Design
In addition to the electrical components, the overall system design (system chassis and other
hardware) has been adapted for safety and ease of adapter installation and removal. Chassis
design changes include quick-release latches on the adapter slots to allow fast and easy removal
and insertion of adapters; wider slot spacing and flexible slot separators to allow users to remove
and ins ert a d apters without el ectri cally cont acting (shortin g ) other compon ents; and a top acces s
shi eld that allows users access to adap ters yet prevents access t o ot her int ern al component s .
Thes e d es ign changes meet or exceed all regul atory safet y stand ards .
System Software
PCI Hot Plug technology is supported by Microsoft, Novell, and SCO. While Compaq has
worked to ensure that each OS is compatible with the PCI requirements, user interface
applications may vary from one OS to another since each user interface is optimized for that OS.
Each OS supplier has defined interface layers between the hot-plug hardware and the OS kernel
to support PCI Hot Plug technology.
Hardwa re an d Software Con trol
In a typical scenario in which the administrator adds an adapter to an empty slot, the following
steps occur whi le th e system is running:
1. The administrator prepares the slot for installation of the adapter by opening the appropriate
slot releas e lever and removing th e e xpa nsi on slot cover.
2. The administrator installs the adapter into the appropriate expansion slot.
3. The administrator closes the slot release lever.
The controller communicates with isolation devices on the PCI bus to electrically
The controller recei ves a comma nd fr om the OS to power up or power down a single
(cont.)
The hot-plug controller also governs the slot LEDs. In Compaq’s
This feature is available only on Compaq’s latest PCI Hot Plug
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4. The administrator uses the PCI Hot Plug Button or the software user interface to notify the
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OS that power can be applied to the slot. The green LED flashes while the OS performs the
power state change.
5. The OS turns on power to the slot and either automatically locates and loads the appropriate
device driver or prompts the administrator to locate and load the driver.
Adapters and Device Drivers
Most industry-standard PCI adapters can be used without any modifications. For industrystandard PCI adapters to have hot-plug functionality, however, new features must be added to the
device drivers .
Leading IHVs committed to modifying their device drivers to be hot-plug aware include 3Com,
Adaptec, Dialogic, Digi International, Mylex, QLogic, AMI, Madge, SMC, and SysKonnect. The
standardization work with the PCI SIG has encouraged the proliferation of hot-plug aware drivers
for third-party devices. In addition, Compaq has developed hot-plug capable drivers for its own
leading PCI server adapters.
Compati bility Issues
PCI Hot Plug technology addresses compatibility concerns by using standard PCI adapters. A
hot-plug system requires a hot-plug platform, a hot-plug OS, and hot-plug adapter dri vers. A
system can include any combination of hot-plug and conventional versions of each of these
components, including a mix of both hot-plug and conventional adapter drivers. However, a
particular a dapt er can be hot-plugged only if all three components for that adapter support h otplug operation.
A hot-plug platform supports loading a conventional OS. Th e system behaves as a conventional
system if no hot-plug software is loaded. Hot-plug OSs are designed to load and execute on any
platform. If no hot-plug controller is found on the platform, then the OS will not permit the user
to perform any hot-plug operations at the user interface.
Hot-plug OSs generally require driver modifications to support full hot-plug capability. However,
as with any driver revision, the OS will often support previous generations of drivers.
Furthermore, in some cases, the new driver can be loaded onto the previous version of the OS. If
a conventional driver is loaded onto a hot-plug OS, or vice versa, the driver will continue to have
the same capability it always had in the conventional application. However, the adapter cannot be
hot-plugged unless both the driver and the OS support the hot-plug operation.
ONCLUSION
C
With the introduction of PCI Hot Plug technology, Compaq once again set the standard in highavailability and fault-tolerant solutions for the enterprise. PCI Hot Plug offers unprecedented
server availability by allowing users to replace, upgrade, and add PCI adapters to the PCI local
bus without powering down the server. With the release of the ProLiant 6500 and ProLiant 7000,
Compa q made t he chassis and electr onics des ign changes r equired for safe and effi cient removal
and insertion of PCI adapters without powering down the server. Next-generation PCI Hot Plug
features are included in Compaq’s newest enterprise server, the Pentium II Xeon Model of the
ProLiant 7000, released in Jun e 1998.
PCI Hot Plug technology brings significant advances to the other high-availability solutions
Compaq currently offers. By bringing this technology to the market as an open, industry
standard, Compaq continues to strengthen its position as a leader in enterprise computing.
(cont.)
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