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My Vintage Computer Virtual Museum and blog page.

IBM PS/2 Model 25 (8525) “8086”

My IBM PS/2 Model 25 (added to my collection in 1997)

  • NEC V30 – 8mhz (originally Intel 8086)
  • 640kb RAM
  • 400MB SCSI (on IBM FRU’d Future Domain TMC-841 card with BIOS)
  • SMC 8Bit 10Base-T NIC
  • Mono MCGA graphics (320×200@8bit, 640×480@1bit)
  • MS-DOS 6.22 and Windows 3.0

I went with SCSI card and SCSI Hard drive since there are only two ISA expansion slots, The SCSI card gives the possibility of external SCSI expansion (more HDs, CD, Jaz, etc…)

I need to update the photos, they still show the 20MB ISA HardCard in place instead of the SCSI controller, and the 2nd floppy drive where the SCSI hard drive now resides.  I have also tapped the power supply lines to the motherboard to add a Molex power connector for the hard drive.



4 Comments

  1. Lorenzo says:

    Hey man, I’m curious, how did you do this?

    >> I have also tapped the power supply lines to the
    >> motherboard to add a Molex power connector for the hard drive.

    Thanks,
    Lorenzo

    • Ryan says:

      I probed the power wires with a multimeter and found which ones were +5V, +12V, and ground and tapped them and added a 4 pin molex to power the drive. When I have some free time, hopefully in the next few weeks, I will add some detailed photos of the mod.

  2. Matt says:

    Hi, I have the same PC, a model 25 with a siemens 8086 and 640kb of memory, its hard drive died (it finds its controller card but not the hard drive), I’m wondering if you had any trouble installing windows on it, since in the box of windows 3.0 (with 720kb floppys in it) says it requires a 286 or higher, and is extracting power from the psu necessary with the hardcard?

    • Ryan says:

      I’d suggest an XTIDE card, and then a Compact Flash memory card (with a $0.99 IDE>CF adapter) as storage, that’s my preferred method these days, a lot more reliable than any ancient 8-bit hard drive.
      Yes, Windows 3.0 will install on a Model 25 with some caveats, the MCGA/VGA video drivers need SOME 286 instructions, this can be worked around by installing an “NEC V30” CPU in the model 25, it’s not a 286 upgrade, and won’t speed things up much, but it’s just enough to trick some things into working. With the stock 8086 CPU you should still be able to install, however, you would be limited to CGA graphics.

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