Model  5550  ( 386 class ) 

PS/55 5550-V24

General information
  Video ( For S and T models )
  Hard Disk interface
    Stage-1 ( 16MHz/20MHz ) Planar 
    Stage-2 ( 16MHz/20MHz )  Planar 
    V0/V1 (25MHz ) Planar
    V2 ( 25MHz )  Planar
  CPU upgrade
  Industrial model

General information
Japanese variants of PS/2 8570. 
5550-S/T, the first Desk Top model of  PS/55 line, were introduced to the market in Apr.1988 together with 5570-T ( 8580-20MHz analogous ). 5550-S/T  were basically same with PS/2 8570.  IBM  Japan  modified 8570 in some way. A most distinctive difference was the number of  MCA slots.  50-S/T has four MCA slots. 
The 4th slot was added for Japanese Display Adapter to handle Japanese characters on PS/2. 
Thus 5550 planar was wider than that of  PS/2 and, as a matter of fact,  the body was also wider  than 8570.
Except the width, 5550 and 8570 were almost same cosmetically. 
The planar of earlier models of  S and T had some problem regarding BUS Mastering feature and those planars were called Stage-1 and the models with free from this problem were called Stage-2.  So there should  be 4 types of  planars for S and T models and another one ( or two )  for  25MHz version.

    Easy way to identify stage-1 and stage-2 . 
    If  the Power SW lever is RED,  most possibly it's Stage-1.
    If  the Power SW lever is WHITE,  maybe it's Stage-2.

   Identifying with serial numbers.
   Even if  the Power SW is white,  systems with following serial numbers belongs 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

 Brief Chart of 5550 and Industrial 5500 models based on PS/55 System Guide 
    O: means the model is listed in the Guide Book
    + UG: means 486DX upgrade option is also listed
5550-S 5550-T 5550-V0 5550-V1 5550-V2 5502-S/T 5502-TG 5502-V2 5502-VG
O + UG
 S1 O
 T1 O
O + UG
 S1 O
 T1 O
O + UG
O S1/T1
 S1 O
 T1 O
O S1/T1
O S1/T1
O + UG

Most possibly switch over to Stage-II from Stage-I was made around May to Jul in 1990. 
As for 5530,   5530-T04/T08 ( Stage -II )  and 5530-S12/S14 (  ZSX on Stage -II  ) were listed in 1990 Nov. edition. 

 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. 

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.

  P/N               capacity          Remarks
  65X1211        2MB                5550-S/T 
  65X1212        4MB                5550-T.  Double-decked shape. 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, ESDI ( roughly speaking ). 

  There were various types of planar for 386-class 5550 
 Model  CPU  Planar Level  MCA Slots
 S  16MHz  Stage-1 & Stage-2  4 Slots
 T  20MHz  Stage-1 & Stage-2  4 Slots
 V0/V1  25MHz  not sure, most possibly 4 
 V2  25MHz  5 slots, No VGA chip  on the planar

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

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Stage- 1 Planar ( 16MH/20MHz)
Following outline is a stage-1 T planar.  Don't know how it differs from Stage-1 S planar. But most possibly these might be same except OSC Y5.
Following stage-1 20MHz planar  looks like 8570 type 1 planar

20MHz T Planar  P/N 65X1377,   EC 341537S

J3  Mouse  Connector
J4  Key Board Connector
J5  Speaker
J8  FDD/HDD Riser Connector
J9  16 bit MCA Slot ( AVE )
J10 32 bit MCA Slot
J11 32 bit MCA Slot
J15 16 bit MCA Slot ( AVE )
J21 Parelel
J22 Serial
U1     LM340
U8     72065L / NEC D72065L
U13   PIO / 72X8299
U16   8042 / 72X8455 ( BIOS ? )
U70   NS16550 / NS16550AV
U111  27512 / 23F3012
U113  IMSG170 / IMSG171P-35
U115  VGA / 90X8941
U128  27512 / 23F3013
U154  80386 / i80386DX
U159  80387 co-pro socket
U168  DMA / 90X8134
Y2  25.175MHz
Y3  1.8432MHz
Y4  28.322MHz
Y5  40.0000
Y6  32.0000
Y7  14.318MHz


Stage-2 Planar ( 16MHz/20MHz )
Recently I had a chance to see stage-2 20MHz planar and noticed it is totally same with my Stage-2 16MHz planar except installed OSC Y1 and planar P/N. 
  1. Aside from the fact that 5550 has 4 MCA SLOT,  Layout of Stage-2 planar is different from  that of  8570 in following points. 

  3. 5550 Stage-2 planar has only one SIMM socket on the planar.  another 2 sockets are placed on the Expansion card which is connected to the planar through  J3.

  5. BUS riser J7 is moved left ( moved downward in the outline below ),  hence HDD/FDD riser is different  from stage-1 model and that of 8570 type-1 ) 



  7. Speaker/Battery connector is not a riser type. SP/BT ASM is connected through wire and a male plug like  8580.
  8. ZIP VRAMs  are directly mounted on the planar.

 See below and compare the planar with 8570 Type-1 outlined by by Louis.

    Stage-II  planar;  P/N  38F6776 for S( 16MHz ) and  54G1612 for T ( 20MHz )
  J1 Power connector edge card
  J2    Keyboard
  J3    Mem expansion connector
  J4    Mouse
  J6    Parallel
  J7    Bus Riser
  J8    DB25 serial
  J9    HD15 Video
  J10,11 32-bit slot 
  J13  16-bit AVE slot
  J14  Speaker/Battery connector
  J15  16-bit AVE slot
  U10  NEC 72065L
  U20  33F8602/FDC
  U21  NS16550AFV/UATR
  U22  33F5946/CPUGA
  U23  33F5944/MEMCTRLGA
  U31  33F5938/IOCTRLGA
  U32  38F6972/EPP3GA
  U38  N8042A/90X9298
  U51  LM339
  U52-57  M5M446AM--12(VRAM)
  U43-44  ditto
  U61  57X4211
  U62  90X8134
  U64  90X8941/VGA
  U74  80386DX-16
  U75  BIOS
  U83  co-pro socket
  U84  MC146818
  Y1    32MHz for S, 40MHz for T

    SYSTEM  MEMORY  EXPANSION  CARD  for  5550-S/T stage -2  planar

J1   102P connector to Planar J3
J2   MEM location 3  ( 2MB/4MB memory slot )
J3   MEM location 2  ( 2MB memory slot ) 
U1  LS244  ( SN74LS244N )

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V0/V1 ( 25MHz ) Planar

     --- Not Available Now -----

V2 (25MHz) planar
As a matter of  fact,  I have not actually examined complete V systems ever.   I just have a V2 planar.   When I draw outline of the planar,  I noticed that 25MHz V2 planar doesn't have onboard VGA.  Man, this planar has 5 MCA slots and, to my surprise, there are solder pads for another 16-bit slots!
BUS riser slot J6 is shifted to the left comparing S planar I have.  It means there should be more than three types of  BUS Riser Card.  Locations of  BUS riser connectors are different with each other.


     25MHz V2 planar 


J1    Power connector edge card 
J2    Mouse 
J3    Connector ( CPU sub-board ) 
J4    Keyboard 
J5    Parallel 
J6    Bus riser ( watch the location ) 
J7    DB25 serial 
J8    Memory slot #2 
J9    Memory slot #3 
J11  Memory slot #1
J10  Solder pads for 16-bit slot 
J12  16-bit slot 
J13  32-bit slot 
J14  BVE 32-bit slot 
J15  32-bit slot
J17  AVE 32-bit slot
J16  Speaker connector
DL2  TQW-100
U14   90X8134
U15   N8042( 90X9298)
U41  56F7502/ISERE
U46  72X8299/PIO
U66  57X4311
U73  NEC D72560L
U77   NS 16550
BIOS P/N 79F5325
Y1  32.0MHz
Y2  14.3MHz 
Y3  40.0 MHz
Y4  1.8432MHz

      CPU Daughter Board
        Main differences between 8570 sub board and 5550-V2 sub-board are
        1)  Pin orientation of 387 co-pro
        2)  Planar-daughter board connector. 


        From 5550-V2 system guide; 
           One 4MB SIMM was originally installed, expandable up to 16MB on the planar.
           Option SIMM's are
                1) 4MB     P/N 79F2536 
                2) 8MB     P/N 79F2500 ( only one module can be used on a planar )

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

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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 
     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 
 80486-25Mhz Processor Upgrade Kit ( P/N 57F0085 ) was listed for 5551-V0x model.

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. 
 Type  CPU
Option Slot
 S01  16MHz
  16MB    --------
 S11  16MHz
 T19  20MHz
  16MB    30MB
 T1A  20MHz
  16MB    60MB
 T1B  20MHz
  16MB  120MB
 TFx  20MHz
 Poss same with TGx
 TGA  20MHz
  16MB    60MB
 4 *
 TGB  20MHz
  16MB  120MB 
 4 *
 V2A  25MHz
  16MB   80MB
2 ( half )
 V2B  25MHz
  16MB  160MB
   2 ( half )
 VGA  25MHz
  16MB    80MB
 VGB  25MHz
  16MB  160MB


Number of Option Slot
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 16bit 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 16bit 6th slot shown in outline of 5550-V2 planar. 5550-V2 planar has four 32/16bit slots including x1 AVE and x1 BVE slot. But above diagram shows 5500-V have three  32/16bit slots and two 16bit slots.   If 32/16bit BVE slot was occupied with a Display adapter, total MCA slots would be SIX including two of 16bit slot.   Would like to see the planar.

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