8556 / 8557 Planar

SX, SLC & Ultimedia M57 SLC

rf855657.exe 8556/8557 Reference Disk v2.10 (zipped image)
   Reference disk supports SLC2/SLC3 upgrades.
rf855657_v123.zip Reference Disk v1.23 (31 Jan 1992, 10G6297) [P]
   Old version! Includes diagnostics. Cleaned up image. (thx to John Horvath)
rf8557um_v123.zip Ultimedia M57 SLC Reference Disk v1.23 (12 Dec 1991, 10G4222) [P]
   Possibly not the latest version. Includes diagnostics. (thx to John Horvath)
rf8557um_v123_alt.zip Ultimedia M57 SLC Reference Disk v1.23 [P]
   Same contents as above except for 4 bytes in the boot sector. (thx to John Horvath)
rd855657.exe 8556/8557 Advanced Diagnostics v2.04 (zipped image)

191-078 PS/2 MODEL 57 SX (8557-045 AND 049)
192-059 PS/2 ULTIMEDIA MODEL M57 SLC (8557-259)

486SLC CPU Upgrade
486SLC2 CPU Upgrade
486SLC3 CPU Upgrade
Cached CPU Upgrade

8556 / 8557 Planar
   Early SX Planar
   Later SX & Early SLC Planar
   Late SX & SLC Planar
System Firmware
   ROM Images
Riser Cards
VRAM Functionality?

8556 / 8557 Planar

Early SX Planar

386SX 20 MHz: FRU P/N 84F7994, P/N 04G3815 [P] (photo from UMMR)

F3 Keyboard/mouse fuse
J1 Mouse port
J2 Keyboard port
J3 Parallel port
J4 DB25 serial port
J5 HDD15 video connector
J6 C60 External SCSI port
J8 Pads for 2-pin jumper
J7/J18 Password-override jumper
J9-11 72-pin SIMM socket
J12 Pads for 3-pin header
J13 MCA riser slot
J13* Pads for 3+1-pin SCSI diag. header?
J14 44-pin floppy connector
J15 50-pin SCSI connector
J17 Power-supply connector P1
J18 Control-assembly connector
J19 Power-supply connector P2
J20 Pads for 6-pin header (+key)
LC8,13 3-pin PCB module (bodge)
OS1 28.3220 MHz osc (SVGA)
OS2 41.5390 MHz osc (SVGA)
OS3 32.0000 MHz osc
OS4 22.1184 MHz osc (UART)
OS5 14.3181 MHz osc (adapters)
OS6 25.1750 MHz osc (SVGA)
OS7 Pads for 44.9 MHz osc (SVGA)
OS8 40.0000 MHz osc (CPU)
OS9 24.0000 MHz osc (FDC)
OS10 Pads for 40 MHz osc (CPU?)
R149 PTC fuse
RT1 SCSI Termpack "T-Res"
U15 CXK58267AM-12L 32Kx8 SRAM (NVRAM)
U16 Pads for DIP-8?
U17 85F0120 SVGA #2
U18 Inmos IMSG171P-50 RAMDAC
U19 Dallas DS1210S NVRAM controller
U20 Dallas DS1285Q RTC/CMOS
U21 91F7490 I/O controller?
U22-25 64Kx16 DRAM (video)
U28 64F4760 SCSI ctrl. "Jalpa" (local bus)
U29,54,60 "Spare"
U30 84F7985 SVGA
U35 Siemens 8032B-16 MCU (SCSI)
U36 SCSI microcode ROM 92F1211
U41 121-pin upgrade/387SX socket
U43 Pads for 9-pin part
U52 82077AA Floppy controller
U58 92F1495 System controller?
U59 i80386SX-20 or IBM 386SLC-20 CPU
U61 04G3806 or 10G7706 PAL
Y1 32.768 KHz xtal (RTC)

J7 has a little sticker over it that says "J18".

J13* Pads for 3+1-pin SCSI diag. header? Possibly the same pinout as J22 on the 9556/7 planar. If correct, this port can be used to access the Serial Console.

LC8,13 3-pin PCB module; Soldered in place of ferrite beads and accompanied by a set of bodge wires (and most likely cut traces) on the solder side (thx Louis). The modules intercept the -REQ and -ACK signals going from the SCSI controller to the internal and external SCSI connectors. Each PCB module contains a mix of active and passive components. It's unknown how exactly are the two SCSI signals manipulated. The LC8 PCB is P/N 92F1551, the LC13 PCB is P/N 92F1552. Later boards have dedicated positions for these modules (with one of them seemingly implemented directly on the board).

U22-25 Toshiba TC511665Z-80H (or BZ-80) 64Kx16 DRAM 40-pin ZIP video memory. See HERE.

U41 The 121-pin PGA socket can be used to install either a CPU upgrade module or 68-pin PLCC socket for 387SX or compatible math coprocessor.

These early boards have a rework in the processor area involving CPU pin 4 (and possibly one other), PAL U61 and resistor network RN8. See detail photos HERE and HERE (thx Louis). This should not be confused with the CPU rework wires present on Early SLC Planars.

Later SX & Early SLC Planar

386SX 20 MHz: FRU P/N 84F7994, P/N 10G4876
386SX 20 MHz: FRU P/N 79F7211, P/N 95F3564 (FRU sticker over silkscreen) [P]
386SLC 20 MHz: FRU P/N 85F0298, P/N 10G5020 [P] (SuperVinx photos)

Same as the Early SX Planar above with some layout differences. Notably:

LC8,13 Ferrite bead (not marked on the outline)
J21 3-pin PCB module
J22 Pads for 3-pin PCB module?

The SLC variant has a set of four bodge wires in the CPU area involving pins 44, 46, 47 and 30 (?). This should not be confused with the CPU rework wires present on Early SX Planars.

Late SX & SLC Planar

386SX 20 MHz: FRU P/N 84F7994, P/N 92F2513 (SuperVinx photos)
386SLC 20 MHz: FRU P/N 85F0298, P/N 10G7645 (SuperVinx photos)

Same as the Later SX & Early SLC Planar above except for:

JP94-97 0-ohm resistors (SLC) or pads only (SX). This replaces the bodge wires from the Early SLC Planars.

System Firmware (POST & BIOS)

Firmware stored in EPROM.

ROM Images

92F1600 - Unknown date/revision (sticker date 16/09/91)
96F7567 - Unknown date/revision (seen in M57SLC) (sticker date 24/02/92)
96F7568 - Unknown date/revision (same as above?) (seen on Early SLC Planar) (sticker © 1991)
10G5029 - 07 Dec 1991, rev. 9 (sticker date 13/10/92 or 22/05/92)

All are 1x Am27C2048-150JC (U55).

Riser Cards

8557SX Bus Adapter

Dotted area on J1 Solder pads for a BVE segment
J10 Solder pads for a 16 pin header
J2 AVE slot

If you have a fantasy about swapping a Lacuna riser and planar into your 57SX, forget it. The Lacuna riser has two mounting slots where the screws are both horizontal, while the 57 has a vertical screw and a horizontal screw. The lacuna mounting holes at the front don't match.


The 57SX supports up to 16 MB of 70 ns memory (all DMA addressable) on the planar in three SIMM sockets. The memory controller automatically supports enhanced performance via memory interleaving with all 2 MB or all 4 MB SIMMs. One, two or three 2 MB SIMMs provide memory interleaving. Two or three 4 MB SIMMs also provide memory interleaving. The 8 MB SIMMs do not provide interleaving.

Video is provided via the enhanced 16-bit industry-standard VGA.

Supports 720 KB, 1.44 MB and 2.88 MB diskettes.

VRAM Functionality?

> This one has actual sockets installed though, not empty pads...?

Peter says:
   Yeah, most have them, and they are somewhat connected to the video-chip glue logic on the planar. But basically they are non-functional. If you look on the board you will find the same old boring Inmos RAMDAC as on Models 50/60 55/65 70/80, with limited bandwidth. Just enough for standard-VGA or 320x200 / 256 colors CGA mode. And - as said: the machine lacks the video modes in its BIOS AFAIK.

Some of the later Greenock variants of the 8556/8557 planar even lack these sockets and have only soldering spots. That was what my comment referred on.

You might however try to install some chips there for 512K and see if you can enable the mode 2Eh - that's 640 x 480 / 256 colors from a 256K palette at 60Hz vertical / 31.5 KHz horizontal. The system should choke out at Mode 12h (640 x 480 / 16 out of 256K, 60Hz / 31.5 KHz) and 13h respectively (320 x 200 / 256 out of 256K, 70Hz / 31.5KHz).

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

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