rf70486a.exe   PS/2 8570 486 reference diskette v1.06
Xgaopt.exe   Installs updated ('92) SC.EXE, XGA/2, SCSI, SCSI w/cache ADFs, plus updated *.dgs. For 5565, 5657, 70486, 7080, 7677, 90, 95, P70, P75.
70bios.dsk (720K) ECA 092: 8570 Data Modification Patch

188-078 PS/2 MODEL 70 386 (8570-A21)
189-196  PS/2 MODEL 70 486 (8570-B61 AND 8570-B21)
189-102  PS/2 486/25 Power Platform
   The 386 -A61 and -A21 can be upgraded by a 486/25 Power Platform. It uses the same planar, but the processor card has a 386 and a socket for a 387DX.  The only 486 system that supports memory expansion adapters is the model 70 A21

BIOS Images. Use AM27C512-175 C/T or equivalent.
Axx 386 BIOS  33F9987 Odd / 33F9988 Even
Bxx 486 BIOS  64F3125 Odd / 64F3126 Even

Additional Hard-drive Power Connector
Replacement CMOS Battery
Making floppy drive adapter (by Bob Eager)

25MHz Planar
Axx Series
   ECA 021 - 110 Error
   3866 Processor Board
   Axx BIOS P/N
Bxx Series
   486 Processor Board
        486 Processor Board Rework
   486 Power Platform Trivia
   Bxx Series BIOS P/N
Hacking a Bxx

25 MHz Planar  Axx series shown
CR1 LM340T5
E1 Jumper outline
J1 16 bit AVE slot
J2,3 32 bit slots
J9 HDD15
J10 DB25 serial
J11 DB25 parallel
J12 Mouse
J13 Keyboard
J14 Planar power edge connector
J15 Processor card socket
J17,18,20,21 72 pin SIMM sockets
J19 SKR/BATT assembly socket
J19A SKR/BATT assembly header
LN1,2,3,4 Unk
OS1 25.175 MHz osc
OS2 28.322 MHz osc
OS3 1.8432 MHz osc
OS4 14.31818 MHz osc
OS5 40.000 MHz osc
OS6 32.000 MHz osc
U11 N8042AH
U12 NS16550AFV
U9,66,80 Unk
U15 INMOS IMSG171P-35 
U19,34 (4)x NEC D41464-10 ea
U20 15F6864
U31,32 N8259A-2
U57 BIOS Odd
U58 BIOS Even
U72 72X8299 PIO
U73 NEC D72065L
U107 63F7520ESD
U109 57X4111
U123 HM6264ALFP-15T
U143 Motorola MC146818AFN
Y1 32.768 KHz

Axx BIOS  33F9987 Odd, 33F9988 Even
Bxx BIOS  64F3125 Odd, 64F3126 Even

Keyboard Fuse?

PTC (?) marked "221K 100V" in the yellow-brown one associates with a Bourne product. Searching brings up a capacitor, maybe this was a fix for a keyboard or mouse port issue?

E1 Jumper Outline
The two pin header "E1" to the PSU side of U72 (72X8299) and to the front of U58 (even BIOS) may be similar to other comparable systems' "Clear CMOS" jumper.

Since the battery / speaker assembly is used to clear an 8570 CMOS, E1 is redundant (if it is CMOS Clear). IBM would be reasonable not to populate it.

    The 2MB 80ns Parity SIMM is the ONLY one supported by the 8570-Ann and -Bnn BIOSes. Four kits can be installed on the system board to reach the maximum system board memory of 8MB.  The 1MB and 2MB 85ns Parity SIMMs should NOT be used on the 8570-A21 system board.

You can use 65X5806, 65X5806D, or Micron DC 2391 (or is that MBBY9?). The IBM stuff has "masked" SIMMs, where R3 and R4 positions are under the PCB resist. You can only find R1 (open) and R2 (shorted) on the IBM 2MB 80nS SIMMs. Third party SIMMs (like Micron) may have all four PD bit positions available, with R1 open, R2 and R3 shorted, and R4 open.

Further Memory Struggles
WBST writes:

The SIMMs should be installed beginning with J21 and/or J20. I got 215 errors (bad SIMM configuration or timing? And it occurs immediately before any counting, like the 225 error) when starting with J17 or J18 and a single true IBM FRU 92F0104 P/N 6450608 2MB 80ns Parity SIMM.

225 errors occur for invalid/unsupported PD-coding or placement of SIMMs (like some of my tall Hypertec HY4309 8MB 70ns Parity SIMMs with the PD-switches). These tall Hypertecs, even when properly PD-coded, caused my Aox/Kingston 32-bit MCMaster 486(SX)-25 to lock up during memory testing, when installed in J18 and J17, with 2 usable 2MB 80ns Parity SIMMs installed in J21 and J20. The timing characteristics are obviously quite crucial for SIMMs in this planar. Also, my BIOS ROMs have earlier P/N labels than those quoted on your page - 33F5825 and 33F5826 (c) IBM 22/11/88. So, I don't know if the SIMM socket placement etc. gets better with the later BIOSes, as yet.

8570-25MHz Models
A61 - 386-25 w. 64kb cache, 2MB, 60MB, 1.44
A21 - 386-25 w. 64kb cache, 2MB, 120MB, 1.44
B61 - 486-25, 2MB, 60MB, 1.44
B21 - 486-25, 2MB, 120MB, 1.44

The VGA port supports graphics and text modes including 640 x 480 graphics, 320 x 200 graphics in 256 colors, and 720 x 400 text, and maintains compatibility with Color Graphics Adapter (CGA) and Enhanced Graphics Adapter (EGA) modes.

J19 Header is Edgecard
  Speaker / battery connector is a 6-pin (2x3), rectangular plug on Type-2 (-061/-121) planar, but is a 3-pin edge-type connector for the J19 socket on the Type-3 (-A21/-B21) planar.

NOTE: If you look above J19, there are solder pads for J19A, which may have been for the older Speaker/Battery assembly.

ECA 029 8570-Axx, Bxx Bus Master Errors
   Some 25MHz system boards may have problems with BusMaster cards like the IBM SCSI adapter as well as others (AOX).  If the card fails to operate properly, examine the barcode label on the system board. If the board has a prefix of B1HC"A", through B1HC"H", replace the board with Part Number 15F7657. [ed. if you can...]

ECA 021 - 8570-A21 110 error 
    8570 model A21 system boards P/N 15F7657 can be replaced. The ECA will be performed at customer request, while servicing the system for any system failure, or if a POST error 110 with five question marks occurs after a memory upgrade. 

ECA 092: 8570 Data Modification Patch
  PHYSICAL CHECK:  This ECA applies to all 25MHz 8570 systems that contain an 80MB or 160MB hardfile that are running DOS or OS/2.  The 8570s that contain those hardfiles are Models A81 and A16 and upgraded 486 Models B81 and B16.
.  It is provided to address a potential problem related to the transfer of data from the hard disk.  SEE ECA092. 70bios.dsk (720K) Installs abios file for use under OS/2 or DOS only.

The original pics for the Power Platforms came from Pete Rickard. Thanks! (Damn hard holding on to the bottom of the earth when typing!)

386 Power Platform FRU 15F7659
  Sorry, I know there never was an option called that...

J1, J2 Reverse of header
U13 387DX-25 Math co-pro
U14 386DX-25
U15-22 MT  5C6408-25
U24 50.0000 MHz
U28 82385-25 Cache controller

Axx 386 BIOS  33F9987 Odd / 33F9988 Even

Bxx Series BIOS
Bxx 486 BIOS  64F3125 Odd / 64F3126 Even

486/25 Power Platform FRU 64F0123 (?)

J1, J2 Reverse of header
U12 50.0000 MHz
U20 486DX-25

  NOTE: Don't be surprised if your 486 Processor board has yellow rework wires on it, mine does and it is marked "Good".

 486 Processor Board Rework

Original image from ebuy seller nyce-distribution.

486/25 Power Platform Trivia
       The Model 70 386 (8570-A61 and 8570-A21) can be upgraded to the Model 70 486 by the installation of the 486/25 Power Platform. The 486/25 Power Platform was previously announced in Product Announcement 189-102, dated June 20, 1989.
   The 486/25 Power Platform is an optional upgrade kit for the Model 70 386 (8570-A21) that significantly increases performance by replacing the existing 25MHz 80386 microprocessor with a new 25MHz i486 microprocessor.  In addition to the new 486/25 Power Platform, the kit includes two EPROM modules to upgrade the system board of the 8570-A21 to support the 486/25 Power Platform.

Upgrade Bxx Series
From Tam Thi Pham
   It *is* possible to beef up the Model 70, with just a tad bit of work. The 8570-B21 will run the  Kingston Turbochip (133MHz) nicely if you upgrade the crystal on the CPU card to 66MHz.  There's a slight issue with clearance for the CPU fan, and it requires that you shave away a bit of  plastic from the underneath side of the top-level drive mounts. Either that, or you could fabricate  your own low-profile heatsink device of some sort. I'm still figuring out all the logistics for an elegant solution.
   Now, the heatsink on the 486DX2-66 Overdrive already has a nice low-profile, and allows that  chip to mount in directly as is for an easy upgrade. I'm thinking you'd rather go all the way to  133MHz, though. Please keep an eye out on the newsgroup (and my site, probably) and I'll detail  my Model 70 upgrade experience.

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