8570 Type 3 & 4 Planar

386 or 486 25 MHz

rf70486a.exe Model 70 486 Reference Disk v1.06 (zipped image)
XGAOPT.exe XGA/XGA2 Display Adapter Options Disk (details HERE)
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, with the exception of the ROM chips. The only 486 system that supports memory expansion adapters is the model 70 A21

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

25MHz Planar
System Firmware
   ROM Images
Engineering Change Announcements
386 Processor Board
486 Processor Board
   486 Power Platform Trivia
   Faster 486 CPU

25 MHz Planar Axx FRU P/N 92F0580, Bxx FRU P/N 41G3979 [P]

CR1 LM340T5 5 V reg. (incl. SCP)
E1 Jumper outline
J1 16-bit MCA slot w/AVE
J2,3 32-bit MCA slot
J9 HDD15 video connector
J10 DB25 serial port
J11 Parallel port
J12 Mouse port
J13 Keyboard port
J14 Power supply edge connector
J15 Processor card socket
J16 Floppy/Hard-drive riser slot
J17,18,20,21 72-pin SIMM sockets
J19 Battery/Speaker socket
J19A Battery/Speaker header pads
LN1-4 Unknown
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
U9,66,80 Unknown module
U11 N8042AH Keyboard controller
U15 Inmos IMSG171P-35 RAMDAC
U19,34 4x (!) NEC µPD41464-10 64Kx4 DRAM
U20 15F6864 VGA controller
U31,32 N8259A-2 PIC (cascade)
U57 BIOS Odd
U58 BIOS Even
U72 72X8299 PIO
U73 NEC µPD72065L Floppy controller
U107 63F7520(ESD) DMA controller
U109 57X4111
U123 HM6264ALFP-15T 8Kx8 SRAM
U143 Motorola MC146818AFN RTC/CMOS
Y1 32.768 kHz xtal (RTC)

J19 6-pin (2x3) card-edge connector for the Battery/Speaker assembly. If you look above J19, there are solder pads for J19A, which may have been for the alternative 6-pin header speaker/battery connector (used on the short Model 50/70 planars and also in Model 60/80).

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

8570-25MHz Models

  • A61 - 386-25 w/ 64 KB cache, 2 MB RAM, 60 MB HDD, 1.44 MB FDD
  • A21 - 386-25 w/ 64 KB cache, 2 MB RAM, 120 MB HDD, 1.44 MB FDD
  • B61 - 486-25, 2 MB RAM, 60 MB HDD, 1.44 MB FDD
  • B21 - 486-25, 2 MB RAM, 120 MB HDD, 1.44 MB FDD


The 2 MB 80 ns 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 1 MB and 2 MB 85 ns 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 80 ns 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 (from WBST)

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 2 MB 80 ns Parity SIMM.

225 errors occur for invalid/unsupported PD-coding or placement of SIMMs (like some of my tall Hypertec HY4309 8 MB 70 ns 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 2 MB 80 ns 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.

System Firmware (POST & BIOS)

Firmware stored in EPROM.

ROM Images

Model 70 386 25 MHz (-Axx, Type 3)

33F9988 / 33F9987 - 20 Feb 1989, rev. 1, 2x AM27C512-175 (U58 / U57)

Model 70 486 25 MHz (-Bxx, Type 4)

64F3126 / 64F3125 - 01 Dec 1989, rev. 0, 2x AM27C512-175 (U58 / U57)

Engineering Change Announcements

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 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 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.

386 Processor Board FRU P/N 15F7659, P/N 64F3703

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

486/25 Power Platform FRU P/N 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" (photo from ebay 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.

Faster 486 CPU (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. <snip>

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

Ardent Tool of Capitalism is maintained by Tomáš Slavotínek.
Last update: 08 May 2024 - Changelog | About | Legal & Contact