Model 5550   ( 486 class ) 

   5551-N Specification
   51-N Planar
   Expansion Slot
   4 Mode FDD
   Hard Disk interface ( Spock)
   Rear I/O
   Body Design
   Clock Rodding 
      5551-R Specification
      51-R Planar
      Hard Disk interface ( EIDE ) 
      Win9x and 51-R/L

     Cirrus SVGA /A

Model 5551-N

5551-N/Y,  general

51-N( and Y ) is SCSI model and it's an IML SYStem. Reference and Diagnostic images are stored in the system partition in a hard drive which is set to ID #6. 

51-N/Y features

  • Synchro Streaming DATA Transfer
  • ECC memory ( not  true ECC ) 
  • Onboard SPOCK SCSI ( with 512KB cache )
  • 4 mode 3.5" floppy drive. 

5551-N Specification
i486DX2-66 ( 8K L1 Cache, Math Co-Pro )
16MB ( ECC, 8MB x2 ) 
8MB ( ECC, 4MB x2 )
3.5" x1 ( 2.88MB/1.44MB/720KB )
 Option Slot ( for User )
 32bit full size x2 ( 1 slot is already occupied with a display adapter ) , 32bit half  x 2
 Interface  K/B port , Mouse port,  RS232C x2 ( 9pin and 25pin ), CRT port,  SCSI 
 Built in SCSI I/F on the planar,   512KB caching SCSI ( SPOCK ! )
 Storage bay ( for user )
 Video Sub System
 PS/55 DBCS Display Adapter /J  ( 1MB VRAM )
 XGA-2 ( 1MB VRAM )
 Kanji Font ROM  8,211 characters of JIS Level 1 and Level 2 and others. 
 360( W ) x 415 ( D ) x 103 ( H ) mm / 9.0Kg
AC Input / PWR consump
 AC100--120V 50/60Hz / 138W MAX
Pre-installed OS
 DOS J5.0
 OS/2 J2.0
 DOS J5.0
 OS/2 J2.0
   5551-NMB ( 16MB RAM,  200MB HD,  XGA-2 )  was equipped with OS2 J2.0 and MicroCADAM2 ( CAD software ).

5551-N System Board
J1    Main  Power 
J2    Speaker Connector 
J3    MCA Riser Connector 
J4    FDD Connector 
J5    50 Pin SCSI Connector 
J7    Power connector for optional Drives 
J11  Overwrite power on pass word 
J14  K/B 
J15  Mouse 
J16  RS232C COM1 
J17  RS232C COM2 
J18  Printer 
J19  60 Pin SCSI Connector 
J20  Power for ? 
J50  Power for CPU Fan 
U1   Solder Pads for 486SX33 
U2   ZIF Socket 
U3   10G7808 (IBM 9314PQ) 
U4   59G1883 
U5   59G1885 
U6   33F6715 
U7   15F6903 
U8   84F9324 
U9   10G4672 
U10 95F4195 
U11 N80C188XL 
U13  DALLAS DS1485S 
U14  M5M5256BFP-12L
U15 10G4891 (M5M27C512AFP-12) 
U16  BIOS one-time PROM
U80/83 74F543D
                  Y902   OSC 66.666Mhz 
                  Y903   OSC 66.666Mhz
                  Y250   OSC 32.000Mhz 
U20  37G2  465F1489 
U100 SCSI 92F2246 
U101 SCSI 92F2247

-N model
   DX2-66 is loaded on a ZIF socket. 
   Planar can take DX4ODPR-100, am5x86 and Cyrix5x86-GP100/120/133 on an appropriate interposer 
   with voltage regulator ( VRM socket is not  prepared on the planar). 

-Y model; 
I'm not sure whether a PGA 486SX-33 is on the socket or a QFP 486SX-33 is soldered on U1. 
ODPDX2-66 is listed as CPU upgrade option for 51-Y. 

Base clock is fixed to 33MHz ( both -N/Y ). 
PODP can not be used on N/Y models. The socket itself can accept PODP but the BIOS doesn't support PODP. 
If a DX2-66 is changed to PODP, system will run, oh no, walk or crawl like a snail. 

Click image to enlarge

72 pin SIMM socket x4.  Total RAM is limited to 32MB. 
The planar  takes  FirstPage , True Parity, 70ns SIMM only ( Standard Industrial Parity  SIMM) . 
ECC/Parity selectable. You can select ECC mode in change-configuration section in  reference menu using true parity SIMMs. 
If Ecc mode is selected, system performance relatively reduces comparing  to normal  parity mode. 
ECC function can be activated only when total RAM size in bank A and bank B are equal. 
    eg 1; A1=8MB, A2=4MB, B1=8MB, B2=4MB
    eg 2; A1=8MB, A2=none, B1=4MB, B2=4MB
    No need to populate SIMMs in matched pair for A1/B1 and A2/B2. 
    Bu I recommend feeding 8MB sticks to all the SIMM slots.

Expansion Slot
Total 5 slots are available in a small slim body using a short height riser card. 
On the riser card, there are 3 slots for full length adapters on the left side( looking from the front panel ) 
and  2 slots for  half length adapters on the right side. 
1 slot( left bottom) is already occupied with a PS/55 Japanese Display Adapter /J or XGA-2 /A according to model and  type. 

     Riser card

       This part is commonly used for 5551-W( 20Mhz) and 5551-R/L ( 33Mhz, EIDE ) models.

No video chip is provided on the planar itself. 
Two types of display adapters were available. 
       DBCS/Display Adapter-J        FRU 07G0446  For models except below. 
       XGA-2 /A  1MB                     FRU 87F4744   For  -NXB/NMB and -YXA 
One of these adapters is loaded at slot # 6 ( left bottom facing to the system from the front .) 

4 Mode FDD: Star marked 2.88MB  4 mode drive x1. 
The drive detects 2.88MB(2ED), 1.44MB(2HD), 740KB(2DD)  and 1.2MB(2HD) Japanese special mode. 

  Something about 1.2MB ( Japanese special mode ) ;  translated from 5551-N Quick Reference
  In order to read and write 1.2MB formatted floppy, special device drivers should be installed for DOS/V,   JDOS
  and OS/2 2.00 and higher environment. These drivers are contained in a "Support Diskette for 1.2MB Diskette "

  For DOS/V and JDOS; 
      Set the driver disk in  A drive, move to drive A, then type install c: following to DOS prompt. 
      Follow the installation instruction appeared on the screen.
      DOS device driver  $FDD35IA.SYS and format menu, FORMAT12.COM,  will be installed.
      IF you have only one FDD in your system, drive letter D and E will be assigned as 1.2MB drive.
      IF you have two FDDs in your system, then drive letter D will be assigned to the 1st FDD and drive 
      letter E will be assigned to the 2nd FDD as 1.2MB drive.

      $FDD35IA.SYS is in Support Diskette Ver. 1.20 and 1.21. 
      $FDD35IA.SYS has been changed to $FDD12.SYS in Ver. 2.01.

  OS/2 2.00 and higher ;
      Choose OS/2 full screen command prompt. 
      Set the driver disk in A drive, move to drive A,  then type install c: and press enter key. 
      OS/2 device driver and format utilities will be loaded under   \OS2 dir in targeted drive.

      OS/2 drivers and utilities;  OS2DASD.DMD,  IBM1FLPY.ADD, FORMATA.COM, DISKCOPY.COM
            CONFIG.SYS will be automatically amended and following  two lines will be added.

            REM --DrvInst--BASEDEV=IBM2FLPY.ADD

      FORAMTA.COM under OS/2
      Once these drivers are installed onto your system, use FORMATA.COM instead of original 
      FORMAT.COM for formatting not only 1.2MB but also for 2.88MB, 1.44MB and 720KB.
      You can get detailed information in HELP menu with typing  FOAMATA  without parameter.

Hard Drive interface ( Spock )
32 bit SCSI I/F is onboard.   SCSI micro code set  is  92F2246/47 and  BUS master control code chip is 10G4891.
512KB cache is ready on the planar. One 50 pin SCSI Header ( not a card edge type ) is on the planar and  one RS6000 style 60 pin connector is on the rear  I/O panel. 

I couldn't configure  F/W SCSI /A, AKA Corvette along with the integrated SPOCK SCSI . 

Depending on model-type,  200MB to 540MB SCSI hard drive was equipped. 
IML drive should  be set to ID=6 and the drive capacity is limited <1GB. 
IBM DPES1080 can't be used as an IML drive.  Actual capacity of the drive exceeds BIOS limit a bit.
Conner CFP1060 might be the biggest one which can be used as an IML drive. ( Actually I used it on my N ).
I don't know why a HDD >1GB can't be used as ID=6 though it has  46/47 micro code combo. 

If you can't find appropriate drive  with 1G capacity, I recommend to use a small drive for IML and choose 
larger drive, say 2G or something, and give ID=5 to such a drive and set it to "C drive" in set-configuration
( I mean "changing boot order " ). 

Hard Drive bay
Two for  3.5" drives (  The bay beside FDD is already populated with a stock SCSI HD  and an optional drive bay locates below FDD  ). 

Unable to install a regular CDD within the case because a full length 5" drive will hit the PSU. 
If you can get a drive for laptop models with SCSI interface and an appropriate connector, and if you don't care for cosmetic appearance, maybe you can set it in  the case. 

Rear I/O panel
 paralle x 1, serials( 25 pin and 9 pin ) x 2,  mouse, keyboard,  1 RS6000 style SCSI connector. 
Slot #1 is assigned for onboard SPOCK SCSI. 

Ref & Diag
   Ref ;    Ver. 1.00/ 1.01/1.11 are available.    Ver. 1.11 is something weird. 
   Diag ;  Ver 1.00 for the ref 1.00/1.01.   Diag Ver. 1.11 is for REF Ver 1.11 

Body Design
Basic design for this machine was established in the model 5551-Wxx  which has  486SX-20.  Drive structures used in 50-W were commonly used  for 51-N/Y/R/L models.  It is impossible to identify model/type at a glance.   You need to check the  label at  the left bottom  of the front cover. 

                     Pic #1                                             Pic #2                                           Pic #3

   Click each image to enlarge

    Pic #1   From top to bottom,  8570-A21, 5551-NAB,  PC720 6860 with 2nd PCMCIA slots,  PC750 6886
    Pic #2   5551-N inner view
    Pic #3   PSU will swing out to right as above.

Clock rodding
A stock  51-N does not accept any higher OSC other than 66MHz. It will stop with 102 error code. 
My 5551-NAB has a modified BIOS ROM and it accepts  80Mhz OSC ( 84Mhz is its limit ). 
With the modified BIOS  ROM and  amd5x86,  it runs  like a champ  in 160MHz  inner clock without  102 error. 

Information from Quick Reference

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Model 5551-R/L 
Appearance is completely same with 5551-N/Y except rear I/O panel. 
Main difference between 51-N/Y and 51-R/L is that 51-N/Y have onboard  SCSI I/F and  IML function  while 51-R/L have E-IDE I/F and *NO* IML function ( reference partition is not  used for 51-R/L. 
 "Set Configuration" should  always be done with the reference diskette).
  • Synchro Streaming DATA Transfer
  • ECC memory ( not  true ECC )
  • IDE HD interface
  • 4 mode 3.5" floppy drive. 

5551-R/L Specification
 Processor  Standard
i486DX2-66 ( 8K L1 Cache, Math-Copro )
 R model ; Pentium OverDrive Processor ( PODP5V83,  P24T so called )
L model ; 486-33/66 Double-clock processor option 
 8MB (  4MB x2 ) 
16MB (  8MB x2 )
3.5" x1 ( 2.88MB/1.44MB/720KB )
340MB ( IDE )
540MB ( SCSI )
340MB ( IDE )
 Option Slot ( for User )
 32bit full size x2 ( 1 slot is already occupied with a display adapter ) , 32bit half  x 2 *1
 K/B port , Mouse port,  RS232C x2 ( 9pin and 25pin ), CRT port
 SCSI /A -II/A 32
 SCSI /A -II/A 32
 Storage bay ( for user )
 0 ( Used for CD-ROM )
 Video Sub System
 XGA-2 ( 1MB VRAM )
 Kanji Font ROM  8,211 characters 
 360( W ) x 415 ( D ) x 103 ( H ) mm / 9.0Kg
AC In-put/PWR 
 AC100--125V 50/60Hz  / 110W MAX
Pre-installed OS
DOS J5.0
 PC DOS J6.1/V
 PC DOS J6.1/V
5551-RMD ( 16MB RAM,  320MB IDE HD,  XGA-2 )  was equipped with OS2 J2.1 and MCADAM/2 ( CAD software ). 
   *1  SCSI Adapter II/A32 ( SPOCK SCSI with 512KB cache ) is equipped for RXE and RED.
        RXE; SCSI HD is hooked to the SCSI /A.  Onboard IDE is left unused. 
        RED; 340MB IDE HD is connected to onboard IDE interface and a SCSI CD-ROM is connected to SCSI/A. 

U1  : Solder pads  for 486DLC 
U2  : ZIF Socket 3 ( Zif socket 1 for L planar ) 
U3  : 10G7808 
U4  : 69G1261 SYS#1 
U5  : 59G1885 SYS#2 
U9  : 10G4672 I/O controller 
U10: 95F4195 
U96: 54G1412 FLASH G/A 
U11: 52G7656 IDE G/A 
U12: N82077SL 
U97: 66G8422 
U98: 66G8423 

J1   : Power Connector ( not used ) 
J2   : Speaker 
J3   : Bus Riser connector 
J4   : FDD connector 
J5   : HD connector 
J11 : Overwrite power on pass word
J50 : No jumpers present ( solder pads only )
JMP5 : Purpose unkown  ( see 5521-Y section ) 
J14 : KB 
J15 : Mouse 
J16 : COM1(  9pin) 
J17 : COM2( 25pin) 
J18 : Printer 
J25 : Power In 
J26 : Power In 
J26 : Power for HD/FDD 
U1  :Solder Pad for QFP( 486-BL2) 
U2  : Socket 3 

I/O PORT:   1 Parallel, 2 Serial ( 9 pins and 25pins), mouse, keyboard . 

Video: depends on machine type, two variations were available. 
       PS/55 DBCS Display Adapter/NI-J            FRU 54G1463 for  models except below. 
       XGA-2 /A  1MB                                       FRU 87F4744  for  -xXx and -xMx. 

CPU and Socket type
R planar has solder pads for  486  QFP package, and  a  486DX2-66  is  loaded on a ZIF socket 3. 
L planar has a 486BL2-66 QFP package and has a ZIF Socket 1 just the same place where a  ZIF
socket  3  is placed on the R planar. 

Same as 51-N/Y .  Support ECC function with true parity 70ns SIMMs.

Power Supply Unit is slightly different from that of 51-N in it's dimension,  but electrical specification  is
almost  same.   PSU for 51-R/L is shorter  than that of 51-N/Y. R/L model has power connectors, J25 and J26, on the planar and at the same time the planar has edge connector J1 at the front right of  the planar. 
Both connectors are electrically connected.   Both 5551-R/L use AT-like power connectors on the planar.

       L planar used in 5530-L lacks J25/J26 connectors. There are solder pads on L planar used in 5530-L . 
       5530-L  uses edge connector J1 to get  DC from PSU. 

Hard Disk interface ( EIDE,  a sort of... )
R and L models have EIDE interface on the planar.  I once used 8.4G 16 heads drive  in my 51-R and 30-L.

     51-R /L was released before EIDE specification was fixed.  It could handle drive larger than 524MB.
     I do not know it's upper limit.  As far as I can see,  51R recognized a seagate 8.4G 16 heads drive 
     which PC750 6886 could not recognize. ( The very same drive once FDISKed using 51-R could be
     used for 6886 but not as a primary *boot* drive but as a secondary drive ). 

Short SCSI Adapter- II/32A with cache ( micro code 44/45 and yellow DIP terminator )  is equipped in 
5551-RXE/RED/RMD and 5551-LEC. 
Genuine SCSI CD-ROM Drive, slim and short depth, is originally equipped  in RED/LEC. 

5551-R is capable to run PODP5V83.  BIOS should be updated to use a PODP. 
BIOS ROM is EEPROM( Flash ROM ) and  only one revision ( for PODfying ) was released by  IBM Japan. 
I think am5x86-133 with a PowerLeap PL586 interposer is the best  choice for upgrading  R  model. 

L planar can't take a PODP because it has ZIF Socket 1 which does not fit to a POD( P24T ).  AMD and/or 
Cyrix on an interposer works fine.

Genuine Option for 5551-L
486-33/66 Double Clock Processor Option P/N  66G0727 was available. 
Intel part JBOX DX2ODP66 could be used. 

Reference and Diag diskette
Following Ref/Diag diskettes are commonly used for 5551-R/L and 5530-L. 
    Ref ;  Ver. 1.21
    Diag; Ver. 1.21

  In order to use a PODP in 51-R,  Flash up program 5551FUP.EXE is required. 
  This exe file will create 
     1) Flash update diskette Ver. 1.30, 
     2) Diagnostic diskette Ver. 1.24 

Clock rodding for 5551-R/L
 70MHz OSC could be used instead of 66.666MHz OSC. Any OSC higher than 70MHz will  cause 102 error. 

Win9x and 51-R/L
1. Unable to use genuine SCSI /A together with onboard EIDE interface. 
    To use genuine SCSI /A, do not use any IDE devices off from the connector on the planar. 

2. If you need to use SCSI devices together with IDE devices,  then  choose Future Domain 
    MCS700, Adaptec AHA-1640 and BusLogic cards.    These cards can be used with it's IRQ other than 14. 

3. IF you use Win98 on your 51-R/L  with a genuine SCSI/A like 1. above ( no IDE drives ) but  you have  an 
    AMD am5x86 in it,  then your 51R/L  will run  in MS-DOS compatibility mode. 

    To solve this problem,  replace AMD CPU to Cyrix 5x86.
    This symptom commonly observed on 51-N and other SCSI models using genuine IBM SCSI /A. 

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Don Peter reported that he succeeded to run Win98SE  on his IML machine. But ( sorry Peter ) I can't 
believe  that  any of IML machine could run Win98(SE) in 32bit disk access with built in SPOCK driver. 
Anyway I don't use Win98/98SE on my PS/55's .   Win98  is too  "heavy" for my good old PS/55's. 

    Additional information ( 2002 01.06 ) 
    Tested Win98 first edition English version on my 9585 xNx. 9585 run in MS DOS compatibility  mode 
    with a DX4-100  and an am5x86-133 ADZ, but  with a Cyrix 5x86-100 it run in full featured  mode. 

    Am I correct?
    During the test I also noticed that 9577 Bermuda ( with onboard SPOCK ) couldn't take a Cyrix5x86 ( this
    is not  OS matter, but the system wouldn't boot with Cyrix ). 
 Updated 2002.10.13

 Peter Wendt replied to the News Group about incompatibility of Windows 98. 
 Peter said; 

   " it appears to be a bug in W98 IOSUBSYS that fails to properly assign  system resources on MCA 
     and  "hebrew and cyrillic versions of Win98 seem to be not affected." 

 Click here for full original text.

 Folks, Do not doubt what Peter sez.   Don Peter has experienced all about MCA. 

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This model is almost same with 5551-R.  CPU is degraded to i486SX-33. 
The most distinctive feature of 5521 is  that a Cirrus GD5428 1MB SVGA /A  was given for YSB and YWB  models instead of PS/55 Japanese Display Adapter.

  5521 Specification 

  • i486SX-33MHz CPU
  • 3 mode 3.5" FDD ( 1.44MB/1.2MB/720KB )
  • DBCS  DA /NI-J for Y1B and Cirrus SVGA for YSB and YWB
  • Support Synchro Streaming Data Transfer
       Modified R/L planar is used for this model  (  QFP IBM486DL2-66  is omitted from U1 ) . 
       486SX33 sits on a Socket-1 at U2. 
       This planar has a jumper block at the location of J6 on R /L planar.  According to quick reference 
       the jumper should be turned on when a double-clock processor option is used instead of a stock 
       486SX33 CPU. 
       Double-clock processor option ( P/N 66G0727 ) is commonly used for 5551-L,  5551-Y and 5530-L .
       There are no such jumpers on these system board (  At least  both 51-L and 30-L  has soldered QFP
       486 CPUs. 

Cirrus GD5428 SVGA /A ( adapter ID : 917A )

     Cirrus GD5428  SVGA /A ( 1MB VRAM standard but upgradable to 2MB) was not available as an 
     "optional part".  It's different from Cirrus SVGA used in Server 500 and is free from "flicker disease".
     There are solder pads for additional VRAM and the circuit is ready for adding SOJ VRAM's. 
     Win95 built-in driver can use full 2MB but NT4 detects only 1MB. 

     Click here for more information about Cirrus SVGA

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