Ardent Tool of Capitalism

Model 5550 386

3070V150.zip Reference & Diagnostic Disk for 5530-S,T/5540-T/5550-S,T,V v1.50 (DOS/V)
   3070V150R.zip Reference Disk for 5530-S,T/5540-T/5550-S,T,V v1.50 (DOS/V)
   3070V150D.zip Diagnostic Disk for 5530-S,T/5540-T/5550-S,T,V v1.50 (DOS/V)
3070V136.zip Reference & Diagnostic Disk for 5530/5540/5545/5550/5570 v1.36 (JDOS)

PS/55 Model 5550-S/T/V Technical Reference (scan by Akamaki; Japanese)
PS/55 Model 5550-S/T & 5570-T ASCII Article (scan by Akamaki; Japanese; Jul 1988)

5550-S/T/V Engineering Changes

IBM PS/55 Model 5550-T Specifications/Option Price List (by Akamaki; Japanese)
IBM PS/55 Model 5550-T (5551-T09) Startup (by Akamaki; Japanese)
IBM PS/55 Model 5550-S/T/V Various Pin Assignments (by Akamaki; Japanese)
IBM PS/55 (5551-T09) SIMM memory expansion does not go well (by Akamaki; Japanese)

General Information Specifications Reference Video (For S and T models) Memory Hard Disk interface Planars S/T Stage I (16/20 MHz) Planar S/T Stage II (16/20 MHz) Planar V0/V1 (25 MHz) Planar V2 (25 MHz) Planar CPU Daughter Board for -V0/V1 and -V2 CPU Upgrade 5502 Industrial Computer

PS/55 5550-V24

General Information

Japanese equivalent of PS/2 Model 70 (8570).

5550-S/T, the first desktop models in the PS/55 line, were introduced to the market in April 1988 together with the 5570-T tower (8580 20 MHz analogous). 5550-S/T were similar to the PS/2 Model 70, but IBM Japan modified many aspects of the original design. The most distinctive change is the number of MCA slots. The Japanese 5550-S/T has four MCA slots, compared to 3 of the Model 70. The 4th slot was added for Japanese Display Adapter to handle Japanese characters. For this reason the 5550 planar is a bit wider than that of the PS/2 Model 70, and as a matter of fact, the body is slightly wider as well (see the badge area on the photo below). The other exterior changes are fairly minor - the type & S/N sticker has been relocated below the power switch, and the LED/switch pictograms are slightly different as well. The base of the chassis is made of a sheet metal instead of plastic.

Front view of Model 5550-T (source)

A look inside (Stage II T Planar) (source)

5551 386 Series Lineup (-S/T/V, original HERE)

Stage I vs Stage II

The planar of early models S and T had some problem related to the bus mastering feature and those planars were called Stage I. The later models that were void of this problem were called Stage II. So there should be 4 types of planars for S and T models and another one (or two) for 25 MHz version.

Easy way to identify Stage I and Stage II:
   If the power switch lever is RED, most possibly it's Stage I.
   If the power switch lever is WHITE, maybe it's Stage II.

Even if the power switch is white, systems with following serial numbers belong to Stage I:
   5551-S09 S/N before 97-19300
   5551-T09 S/N before 97-44700
   5551-T0A S/N before 97-58000
   5551-T0B S/N before 97-93100

Most possibly switch over to Stage II from Stage I was made around May to Jul 1990.

PS/55 System Guide - 5550 and Industrial 5500 Models

Specifications

5551-S0/T0 Specifications (original HERE)

Reference

Ref. Ver. 1.00 to Ver.1.36 are based on JDOS.
Ref. Ver higher than 1.4x are based on DOS/V.
Ver. 1.50 covers most of of all 386 models such as 5550-S/T/V, 5570-T/V, 5540-T, 5530-T.

Video

For S, T and Vo/V1 models

As like as PS/2 8570, PS/55 5550-S/T have VGA chip on the planar. But in order to handle true Japanese fonts, PS/55 Japanese Display Adapter II (with AVEC connector) is equipped with earlier models of 5550-S/T (and 5570-T). VGA port on the planar is covered with a plastic plug.

For V2 model

I'm not sure about a display adapter used for this model. V2 planar does not have a VGA chip and it has BVE MCA slot. Then most possibly Display Adapter B or B-2 might be equipped with V2 model.

Memory

P/N	Capacity	Notes
65X1211	2MB	5550-S/T
65X1212	4MB	5550-T Double-decked. Only one module can be used. This module should be installed at J9 (memory slot #3)
23F2165	4MB	5550-V0/V1. Double-decked
79F2536	4MB	5550-V, 5541-T, 5530-S/T, 5510-T
79F2500	8MB	5550-V, 5541-T, 5510-T

Hard Disk Interface

Same as 8570, DBA ESDI.

Planars

There were various types of planar for 386-class 5550.

I've once heard that S stands for Sixteen, T stands for Twenty and V stands for twenty-fiVe.

S/T Stage I Planar

P/N ? (S - 16 MHz)
P/N 65X1377, EC 341537S (T - 20 MHz)

This planar is also used on the IBM 7561/7562 industrial computer.

U111/128 2x 27512 64Kx8 BIOS EPROM (Even/Odd)
   23F3012 / 23F3013 - PS/55 Model 5550, rev. ?
   65X1506 / 65X1507 - IBM 7562, rev. ?

U112,114,116,124,129,131,134 M5M4464AL 64Kx4 DRAM (video)

Uses the same core logic and general design as the 8570 Type 1 planar.

The Stage I S planar is probably the same except for the oscillator Y5.

S/T Stage II Planar

P/N 38F6776 (S - 16 MHz)
P/N 23F3346, 54G1612 (T - 20 MHz) (photo by Akamaki)

U75 27C1001 128Kx8 BIOS EPROM
   38F6933 - 5551-T rev. 07h / 5551-S rev. 0Ah, 04 Apr 1989

J7 is moved left, therefore the HDD/FDD riser is different from the Stage I model (and that of the 8570).

Important: The original electrolytic capacitors are prone to leaking! If your board is affected by this problem, you should replace the capacitors and clean the board as soon as possible. Otherwise, the leaking electrolyte will inevitably destroy the board! The following radial through-hole electrolytic capacitors are used on the board:
   10 µF 25 V; 20 pcs (leaked, nichicon brand)
   22 µF 25 V; 5 pcs (leaked, nichicon brand)
   47 µF 16 V; 1 pc (not leaked on my sample)
Polymer or tantalum capacitors can be used as an alternative.

This planar uses the same core logic as the 8570 Type 2 planar, the Later P70 planar, and the Type 0 processor complex.

System Memory Expansion Card For 5550-S/T Stage II Planar (P/N 38F6776)

J1 102-pin planar connector J2 "MEM 3" 72-pin SIMM socket (2 MB/4 MB memory slot) J3 "MEM 2" 72-pin SIMM socket (2 MB memory slot) U1 74LS244

V0/V1 (25 MHz) Planar

FRU P/N 23F2146

U12/30 2x 27512 64Kx8 BIOS EPROM (Even/Odd)
   56F7416 / 56F7417 - PS/55 Model 5550, rev. ?

U124,125,128,131,138,139,141,145 M5M4464AL 64Kx4 DRAM (video)

Uses the same core logic and general design as the 8570 Type 3/4 planar and 8580 Type 3 planar.

V0/V1 Floppy/Hard-drive Riser

FRU P/N 94X1574, "INTERPOSER CARD"

F1 3 A fuse — 5 V for drives & Molex
F2 2 A fuse — 12 V for drives
F3 Pads for fuse — 12 V for Molex
J4 Pads for Molex connector

No other components (aside from the floppy drive and DBA hard drive connectors).

Physically compatible with 8570.

V2 (25 MHz) Planar

The V2 planar doesn't have an onboard VGA. This planar has 5 MCA slots and there are solder pads for another 16-bit slot.
The bus riser slot J6 is shifted to the left compared to the S planar. It means there should be more than three types of the Bus Riser Card, as the location of the bus riser connector is different between the boards.

25 MHz V2 planar P/N 79F5325, EC C27264D

Memory

Source: 5550-V2 system guide

One 4 MB SIMM preinstalled, expandable up to 16 MB on the planar.

Option SIMMs:

• 4 MB P/N 79F2536
• 8 MB P/N 79F2500 (only one module can be used on a planar)

Overclocking

A guy once reported that he had changed 50 MHz osc to 60 MHz and system worked without POST error.

CPU Daughter Board for -V0/V1 and -V2

P/N 44F1518

Riser card for HD and FDD

As written in V planar section, there are several types of bus riser cards. I once had two types of riser card but there should be three or more.

CPU Upgrade

I tested following upgrade kits on my S and T models.

1. Evergreen upgrade modules with IBM486BL2 and BL3.
   Cyrix and TI chips could be used on S/T models but not on V models due to 64K L2 cache on the CPU board (I have not examined).
2. Kingston MC master 486 (originally made by AOX).
   I used it on T planar. MCMaster can take a 5x85 CPU but you can't use neighboring MCA slot in order to use 5x86 CPU with a heatsink. Not a good choice for 8570 because it has only 3 MCA slots.
3. PowerBoard
   In order to use a PowerBoard on S (Stage II) model, some adjustment is needed to place the board properly.
   1. Need to adjust location of metal parts for screw holes to keep the planar.
      Location of screw holes at left front edge is different between S and T/V.
   2. a Bus Riser card for FDD and ESDI hard disk for T model.
   3. battery and SP unit for T model.

Genuine option by IBM 80486 25 MHz Processor Upgrade Kit (P/N 57F0085) was listed for 5551-V0x model.

5502 Industrial Computer

5502 is an industrial model number.
Industrial models are numbered as "5500" and each model has unique number such as 5502-S1x, -T1x and so on.

Number of Option Slots

System Guide describes number of Option Slots left for users except already occupied with a Display Adapter. So basically, one slot should be added to the number shown in a diagram.

Model S11 to T1B meet with the rule and one 16-bit AVE slot might already be occupied with a display adapter. Then how it comes that TGA and TGB were noted as 4 + 1? Wonder if these 2 models were not shipped with any Display adapters and use VGA on the planar?

Next question; it seems models Vxx models DO have activated 6th 16-bit slot shown in outline of 5550-V2 planar. 5550-V2 planar has four 32/16-bit slots including 1x AVE and 1x BVE slot. But above diagram shows 5500-V have three 32/16-bit slots and two 16-bit slots. If 32/16-bit BVE slot was occupied with a Display adapter, total MCA slots would be SIX including two 16-bit slots. Would like to see the planar.