PS/55 Processor Complexes

Processor Complex Matrix (PS/2 vs. PS/55)

60-W0x Complex
80-Yxx Complex
60-W1x/W2x Complex
80-W0x/W2x Complex
N / DX2/66 Upgrade Type-B Complex
DX2/66 Upgrade Type-A Complex

CPU Upgrades
Complex Upgrades

Content created by Sandy. Edited by Major Tom.

Processor Complex Matrix (PS/2 vs. PS/55)

   Following chart was originally presented by Mr. NATICA, one true MCA enthusiasts from Japan who helped me in many ways with my PS/55s.

PS/2 CPU PS/55 PS/55 P/N O/D socket Notes
Type 1 "J" 486DX-25 5561-W0x 79F0087 None
Type 1 "K" 486DX-33 5580-Yxx 79F2458 None
Type 2 "H" 486SX-25 5561-W1x 07G3153 Yes
Type 2 "H" 486SX-25 5580-W0x 07G3153 Yes
Type 2 "L" 486DX2-50 5561-W2x 07G3153 Yes, DX2 installed
Type 2 "L" 486DX2-50 5580-W2x 07G3153 Yes, DX2 installed
- 486DX2-66 5580 Option 66G1087 Solder Pads 1) 3)
- 486DX2-66 5561-N 35G2951 Solder Pads 2) 3)

   1) This complex is also called DX2-66 Upgrade Type A.
   2) This complex is also called DX2-66 Upgrade Type B. Originally equipped in 60-Nxx.
   3) Base clock is 33 MHz but is apparently different from "DX2-66 Upgrade 92F0145" (?).

The 66G1087 and 32G2951 processor boards are unique to the Japanese PS/55 machines. No direct PS/2 equivalents seems to exist.

Type A can be used both in 5560 and 5580, while Type B can only be used in 5560.

Type 3 and all Type 4 Complexes are commonly used for PS/55 8595-J and PS/2 Model 95.

60 -W0x Complex 486DX 25 MHz (P/N 79F0087)

Based on the Type 1 platform. Similar PCB, but not identical.

A 256K cache daughter board is available as an option.
No overdrive socket.

The board P/N is different from the 80-Yxx complex, but all parts and chips are the same, except for the oscillator.

This complex can take 31(?) MHz OSC without changing the BIOS.

80-Yxx Processor Complex 486DX 33 MHz (P/N 79F2458) [P]

Based on the Type 1 platform. Similar PCB, but not identical.

A 256K cache daughter board is available as an option (P/N 79F1294, ECC 63993A).
No overdrive socket, no solder pads.

The board P/N is different from the 60-W0x complex, but all parts and chips are the same, except for the oscillator.

EPROM BIOS P/N 92F0145 (really? the photo says 79F0181).

Memory count is very slow, like the 5561-W0x complex.

Easy to upgrade with DX2-66. You can also use DX4-100, AMD 5x86-133, or Cyrix 5x86-100 together with an interposer.

60 -W1x/W2x Complex 486SX 25 MHz / 486DX2 50 MHz (P/N 07G0460?)
80 -W0x/W2x Complex 486SX 25 MHz / 486DX2 50 MHz (REA 19602276?)
(P/N 07G3153, FRU 95F4299, FCC ID ANOIBM486SXB25) [P]

Based on the Type 2 platform. The PCB seems to be identical.

No L2 cache available.

EPROM BIOS 07G0463 (IBM 1981-1991).

Memory count is faster than with the 60-W0x complex.

Installed Processor(s)

5580-W0x, 5561-W1x:
   - 486SX-25 in U8
5580-W2x, 5561-W2x:
   - Earlier models shipped with i486SX-25 in U8 + ODPDX2-50 (ID#06G7015) in U9.
   - Later models shipped with just 486DX2-50 in U9.

Reference Disk

Requires system specific ref/diag disks. 5580-W disks on Model 5580, and 5560 -W1/W2 disks on Model 5560.

I got the following message when creating a reference diskette for this model:

Is "Canberra" code name for the 5580-W? Does "P23T" mean DX4ODP?

DMA Controller

Some Type 2 boards suffer from "an incompetent DMA-chip", more info HERE.

The Japanese "KIT-W2B" has the "bad" 92F1428 DMA chip, yet it works fine with the following CPUs:

  1. DX4ODP-75 with 486SX-25 in the 1st socket.
  2. DX2-66 alone in the 2nd socket (50 MHz internal clock) (huh?)
  3. DX4-100 on an interposer with VRM, alone in the 2nd socket.
  4. AMD 5x86 or Cyrix 5x86 (with voltage interposer) in the 2nd socket.

There is no significant difference between the Type 2 "H" and the PS/55 -W1/W2 complexes. Just the board P/N (or FRU?) and BIOS P/N are different.

60-W2 Identification

My machine is labeled as "5561-W1B" and has a "KIT-W2B" sticker.

The area where P/N is silk screened on the -W1 complex is covered with a "P/N 07G3153" (+ REA number) sticker. There is also a "MPU Upgrade" sticker stuck to one of the blue lock/release levers.

N / DX2-66 Upgrade Type-B Complex (P/N 35G2951, FRU 35G2765) [P]

Based on the Type 2 platform. Similar PCB, but not identical.

Originally shipped with Model 556-N which was introduced to the market in Sep. 1992.

There is no over drive socket on this complex, only solder pads (U9). DMA controller chip (U6) is 34G3517 for N, and 92F1428 for W1/2.

There are at least 2 versions of this complex. While replacing the original oscillator with a 80 MHz one, I've noticed that some of the PCB traces near the oscillator were different. I've also noticed an SMD resistor that is not present on the other board. Both complexes worked fine with the 80 MHz OSC and modified BIOS ROM.

DX2-66 Upgrade Type-A Complex (P/N 66G1087) [P]

U1 74F32
U2 74F125D
U3 74F00
U4 74F04
U6 74F760D
U10,U14-U18 74F244
Y1 66.666 MHz OSC
U5 PA2 59G1883
U7 DMA32 10G7808
U9 486DX2-66
U12 PF2 59G1885
U13 BIOS P/N 66G1095

Memory count is extremely fast.

Support for Streaming Data transfers. Support for 2.88 MB floppies (In BIOS? Shouldn't all complexes have support for this?).

CPU Upgrades

For 60-Wxx, DX4ODP-75 can be used. You can use DX4ODP-100 as well, but it will only run @ 75 MHz.

The N model will take DX4-100, AMD, or Cyrix with an appropriate VRM interposer that lowers the core voltage to 3.3 - 3.45 V. Since the N complex has its CPU socket near the front edge, larger heatsinks won't fit. The same is true for most active coolers as well. But as long as you use the blue plastic air guide as intended, your CPU should get *enough* airflow from the front intake fan.

Complex Upgrades

60-W0/W1 can be replaced to -W2 or -N complex.
60-W2 can be replaced to -N complex.

60-W1/W2 complexes can be used for 5580. Associated ref/diag for 5560 could not be used in this case. Ref/diag for 5580-Wxx should be used together with.

5580 with 60-W0 complex with 5580-Y ref/diag -> No equivalent model, but works fine.
5580 with 60-W1 complex with 5580-W ref/diag -> 5580-W0x
5580 with 60-W2 complex with 5580-W ref/diag -> 5580-W2x

PS/55 Index