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IBM Model 70 and Adaptec AHA-1604 SCSI Adaptor

 Adding the Hardware (Proceed at your own risk!)
This is how to add an Adaptec AHA-1604 SCSI card and SCSI drive to an old IBM Model 70. If you have one with a dead ESDI drive this is the cheapest and easiest way to fix it. The slots in this computer are called Micro-Channel or MCA. The Future Domain MCS-700 is also a good SCSI card but I couldn't find any OS/2 v1.3 drivers for it.

First problem... no power plug for the drive. The floppy drive in my system had the voltages printed right on top of it. The first 3 pins in the top row were 12v, 5v and Ground. The top 3 pins on the other expansion slot were also 12v, 5v and Ground. All I had to do was solder a power plug off an old power supply to those 3 pins.


  • Make sure the soldering iron has sharp clean tip
  • Solder 2 Black (Gnd) wires together
  • Add solder to the Yellow (+12v) wire tip
  • Add solder to the Red (+5v) wire tip
  • Cut all tips so about 1/8" of wire is exposed
  • Check first 3 pins on top right to make sure voltage is correct.
  • Clean soldering tip with wet sponge or rag
  • Add a tiny bit of solder to the 3 pins
  • To solder the wire: 
    • Bring the wire in from the top
    • The end of the wire should butt right into the pin
    • Touch the end and pin with the soldering iron just long enough for the solder to melt together
  • Solder the Yellow wire to pin 1
  • Solder the Red wire to pin 2
  • Solder the Black wires to pin 3
  • Check to make sure none of the pins are touching together
  • Put a blob of hot glue on top of everything to hold the wires securely in place.

Insert the SCSI card into the MCA slot. It only fits in one slot, one way. Plug the 50 Pin cable onto the SCSI cards 50 Pin plug. Make sure the red or stripped wire running down one side is connected to pin 1. Facing the front of the computer in this picture.

Second problem... No place to put a standard size hard drive. A couple of metal brackets and the plastic ESDI bracket will solve that problem.

Use some copper or aluminum flashing. It's easy to cut, drill and bend. Nothing fancy, just 1 bend and 4 holes per side. Attach it the plastic bracket with the 4 screws and 4 nuts. I happen to have 4 lock nuts left over from an RC car that fit perfect.

Make sure the board on the bottom of the drive won't hit anything metal and you have plenty of room to get a nut in there. Put a piece of heavy black electrical tape along the bottom of the bracket to help dampen the vibration between the drive and the computer.

Snap the drive into place and attach the cables. In theory everything should work fine.

 Installing the Software
Before the SCSI card will work, the Model 70 has to be set to recognize it. This requires a bootable Model 70 Reference Disk with the AHA-1640 SCSI file "@0f1f.adf" on it.

Put the Reference disk in the computer and turn it on. It should complain about the SCSI card and tell you what to do. Tell it to Automatically Configure the computer. Just say Yes and keep going until it's finished. If you have other cards in the computer you will need the .ADF file for each of them or they will stop working.

Reference Disk? You can download the reference disk and 1604 .ADF file below. Run the rf7080a.exe program and follow the directions. After you have made the reference disk copy the "@0f1f.adf" file onto it.

  • IBM PS/2 Model 70 Reference Disk 1.12 - Download
  • Adaptec AHA-1604 SCSI ADF Reference file - Download

 Setting up the Drive

The drive may need to be partitioned and formatted before it can be used. Create a DOS boot disk and use FDISK to partition the drive. Then reboot and format the drive using the FORMAT command. This will work for OS/2, DOS and Windows.

 Installing OS/2 v1.13

Arghhh... what a nightmare! :) I had to search for a long time to track down the v1.13 SCSI drivers. Once I found the drivers they wouldn't fit on the OS/2 Installation disk. After 5 or 6 hours of trial and error I finally came up with a method to install everything.

Start by making a copy of the Installation Disk. Boot into DOS and use DISKCOPY to make an exact copy of the OS/2 Installation Disk or it won't boot. This method may not work if the drive was setup to use the HPFS file system. Replace the HPFS.IFS file on the new install disk with a 0K file of the same size. Just make a blank .txt file and name it HPFS.IFS. This will free up enough room on the disk to allow all the SCSI files to fit.

Copy all the SCSI 1604 driver files onto a separate floppy disc. Then copy the real HPFS.IFS file off the original installation disk onto this disk. You'll need this disk later.

Now copy the SCSI driver files onto the copy of your OS/2 Install disk. You need to copy all the files in the DISK0 folder, SHARE folder and 1640 folder. Just copy them onto the disc using DOS or Windows. Now you should be able to boot with the OS/2 install disc and go through the install process. When it's finished leave the disk in the drive and reboot. When the blue screen appears hit ESC and exit to the blinking prompt.

Now insert the SCSI driver disc you made and type SETUP. I added a special SETUP.CMD file to copy all the files onto the hard drive and replace the 0K HPFS.IFS file with the real one. When it's done copying take the disk out of the drive and the hard drive should boot into OS/2 v1.13.

  • Adaptec AHA-1604 OS/2 v1.13 Driver Disc - Download

WARNING: Mouse and Keyboard problem! I came across a problem with my PS/2 mouse and keyboard. I had an MS Mouse and MS Natural Keyboard attached. They both worked fine in DOS but when I installed OS/2 the computer would hang during startup. I had to switch to an old AT keyboard with a PS/2 adaptor before it would boot correctly. You can also disable the MSPS202.SYS file in the config.sys file to boot with no mouse.

Note: I found some other useful information when searching for drivers. If your reference disk won't boot, run this from DOS. It should make it bootable again.

You can press CTRL+A on the main Reference screen to test one thing at a time.

The contents of this page are 2009 Realm
Last Updated (January 1st, 2007)