Introduction helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;1098530389
An easy upgrade path to higher CPU performance is built into S-Series. The OverDrive
Introduction
IntelTM486 Classic S-Series incorporates a high performance SuperVGA solution in an affordable
i486 platform. A wide range of i486TM CPU offerings gives performance flexibility to start and the
OverDriveTM Processor Socket gives a future path to higher performance. An LPX form factor system
design with video, hard disk, floppy control, mouse, and other I/O ports integrated, as well as five
slots and 4 bays provides the expandability needed for traditional desktop PC applications.
The onboard Western Digital 90C31 SuperVGA controller gives solid performance for VGA
applications and superior Windows performance, even at the maximum resolution of 1024 X 768 X
256 colors. This performance is attained via hardware built into the 90C31 which accelerates the
most essential Windows graphics functions.
TM Processor
Socket allows installation of either an i487TMSX to provide power for numeric intensive applications,
or an OverDriveTM Processor, Intel's clock doubling upgrade processor, to significantly improve CPU
performance.
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General Board Layout helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-239213223
A. VGA video Connector (J1)
General Board Layout
B. Parallel Connector (J2)
C. Serial Port 1 Connector (J3)
D. Serial Port 2 Connector (J4)
E. Mouse Connector (J5)
F. Keyboard Connector (J6)
G. Offboard Batter Header (J7)
H. Auxilliary Fan Power Header (J11)
I. Power Connector (J10,J15)
J. 3 ½ - inch Floppy Disk Drive Header (J18)
K. IDE Disk Drive Header (J17)
L. ISA Riser Card Connector (J8)
M. Front Panel Reset Switch Header (J24)
N. Front Panel Keyboard Lock Switch/Power LED Header (J23)
O. Hard Disk Activity LED Header (J22)
P. VESA - Compliant 8514/A Standard Feature Header (J12)
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CPU helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-1389441038
SX running at 20,
CPU
IntelTM486 Classic S-Series provides several different base CPU options; an i486TM
or 25 MHz or an i486DX at 33 MHz. This provides a wide price/performance range to fit a variety of
customer application needs.
The S-Series supports complete i486 CPU functionality. Common features of the three CPUs include
backward compatibility with the 8086, 80286, and i386TM CPUs, burst mode bus cycles, and an
on-chip 8 Kbyte cache. The cache is 4-way set associative and uses a write-through policy, and can
be disabled via software. The i486DX CPU contains an on-chip numeric coprocessor to increase the
speed of floating point operations. This coprocessor is backward code compatible with 387DX and
387SX math coprocessors and complies to ANSI/IEEE standard 754-1985. The i486SX does not
include the numeric coprocessor.
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System Memory helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-1491376660
System Memory
The S-Series memory sub-system consists of three logical banks of SIMM memory. Bank one
supports a single 36-bit SIMM socket, while banks two and three consist of four 9-bit SIMM sockets
respectively. All production systems ship with one 4 MB (1 Mb x 36) SIMM in bank one. This SIMM
can be removed and replaced with a 2 MB (512 Kb x 36) or 8 MB (2Mb x 36) of memory.
Banks 2 and 3 each consist of four 9-bit SIMM sockets and can be populated with 256K X 9, 1M X 9,
or 4M X 9 SIMMs. SIMMs must be installed in the 9-bit sockets in sets of four of the same size and
type, but no other restrictions exist. The maximum memory size for S-Series is 40MBs. For a
complete list of possible memory configurations, refer to Appendix D.
Each bank supports 80-ns fast page mode SIMM memory. Faster DRAM can be installed, however
no improvement in performance will be seen.
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Optional Cache helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;1134761394
An optional cache is designed into Classic. The Opti chipset includes a direct mapped, write back
Optional Cache
cache controller, while DIP sockets for SRAM installation on the motherboard support either 64K ,
128K, or 256K of cache SRAM. For SRAM vendors and installation details, refer to Appendices B
and E.
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Approved SRAM list helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;1904199960
Approved SRAM list
The Classic S-Series can be upgraded with an external cache by adding SRAM components to DIP
sockets on the baseboard. The design requires 20 ns data SRAM and 15 ns tag and dirty bit SRAM.
Installation is as follows. Refer to Appendix B for jumper settings.
Cache Size SRAM Size
Bank 0
U46-U49
64 K
128K
256K
The list below details the part numbers for a 64K, 128K, or 256K cache from several different
vendors.
Device Type Motorola Cypress IDT Samsung Mitsubishi
8 Kb x 8, 15
ns
8 Kb x 8, 20
ns
32 Kb x 8, 15
ns
32 Kb x 8, 20
ns
64 Kb x 1, 15
ns
MEM6264PC15 CY7C185-15PC 7164S15TP KM68685BP-15 N/A
MEM6264PC20 CY7C185-20PC 7164S20TP KM68685BP-20 N/A
MEM6206PC15 CY7C199-15PC 71256S15TP KM68257BP-20 N/A
MEM6206PC15 CY7C199-20PC 71256S20TP KM68257BP-20 N/A
MEM6287P15 CT7C187A-15PC 7187S15P N/A M5M5187BP-15
(4) 8Kb x 8 (4) 8Kb x 8 (1) 8Kb x 8 (1) 64Kb x 1
(4) 32Kb x 8 none (1) 32Kb x 8 (1) 64Kb x 1
(4) 32Kb x 8 (4) 32Kb x 8 (1) 32Kb x 8 (1) 64Kb x 1
Bank 1
U42-U45
Tag
U50
Dirty Bit
U51
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Opti Chipset helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-1920021991
Opti Chipset
The Opti 486SXWB is a three-chip solution for i486TMDX and i486SX ISA-based systems. It includes
an 82C495 System Controller, an 82C392 Data Buffer Controller, and an 82C206 Integrated
Peripheral Controller. Each of these chips functions is detailed below.
Related Topics:
82C495 System Controller
82C392 Data Buffer Controller
82C206 Integrated Peripheral Controller
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Approved Video DRAM helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-379070227
Approved Video DRAM
The Classic S-Series can be upgraded to 1MB of video DRAM by installing four 70ns 256Kx4 Page
Mode DIP DRAM. Below are several vendors and their part numbers.
Texas Instruments TMS44C256-70N
Siemens HYB514256B-70
Toshiba TC514256AP-70
NEC uPD424256
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Performance Upgrade helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-299951445
Performance Upgrade
Upgrades to higher performance are easy using the Performance Enhancement Socket incorporated
into Classic. An i487SX can be added to any of the i486SX systems to provide improved floating
point performance. The S-Series can also be upgraded with an OverDrive Processor, providing
significantly higher CPU performance and numerics capability for i486 systems. For specific details
concerning the upgrade process, refer to Appendix G.
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Board Product History helpexplorer:///@hash-id:CLASSICS.HLP;helpexplorer-main;-1637353270
Board Product History
As of June 15, 1994
Current PBA Numbers
518725-013 i486SX-20 1.00 08.W0
518726-016 i486SX-20 1.00 08.W0
518726-013 i486SX-25 1.00 08.W0
518726-016 i486SX-25 1.00 08.W0
611418-006 i486SX-33 1.00 08.W0
518727-013 i486DX-33 1.00 08.W0
518727-016 i486DX-33 1.00 08.W0
611018-007 i486DX2-66 1.00 08.W0
Related Topics:
Engineering Change Orders
Board Revision History
CPU Current Shipping BIOS
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