Facts

  • Manufacturer: Compaq Computer Corporation
  • Type: Portable computer (dragable)
  • Released: 1987
  • OS: Compaq DOS 3.1
  • CPU: Intel 80286 @ 12 MHz (FPU possible)
  • Memory: 640 KB (upgradable with expansion board)
  • Display: 10″ gas-plasma display
  • Graphics: Up to 640 × 400 pixels monochrome
  • Textmode: 80 × 25 column (ANSI)
  • Sound: PIT (PC speaker)
  • Connectivity: CGA, serial, parallel
  • Dimensions: 41 x 19.2 x 24.8 cm
  • Weight: 9.1 kg
  • Predecessor: Compaq Portable II
  • Successor: Compaq Portable 386

Released 1987: The Compaq Portable III is a PC/AT-clone computer released by Compaq Computer Corporation in 1987. It was advertised as being much smaller and lighter than the previous portable x86-PCs, however it was still quite large by today’s standards. Its street price upon its release was 4999 USD for a model equipped with a 12 MHz Intel 80286, 640 KB RAM, 1.2 MB 5.25″ floppy, 20 /40 /60 MB hard disk, and a 10″ amber colored gas-plasma display or 5799 USD with the upgraded 40 MB hard disk. There was also an optional ISA Expansion chassis allowed for two full length 16-bit ISA add-in cards. Power is supplied using a mains electricity outlet, no battery exists.

Repair and upgrades
Got this one from a college at my job. An error message about inserting the “Diagnostic disk” and “no settings found” on startup. The machine and keyboard also needed a throughout clean, and the keyboard coil cable was “rotten”.

A friend has an vintage PC with 5.25″ floppy drive and he made wrote me a Compaq DOS 3.1 floppy, I’ve also found the diagnostic/BIOS setup software for this model on Internet and copied it to an floppy. This model got no BIOS setuo software built into its ROM and needs to run the setup from disk.

Turns out, this computer got a non-rechargeable battery integrated into an special IC chip “Dallas chip” for storing the CMOS/BIOS settings. No surprise, the battery was long gone. The “Dallas chip” contains a small amount of CMOS RAM and the RTC (clock) as well.

Dallas “RTC” chip: I removed the chip from the main board, luckily it was already in a socket. I used a carpet knife to carefully scrape holes exactly where the ground and plus for the battery are located (above pin 16 and 20 I think). I cut the ground leading to the integrated battery and soldered on two wires for a new battery. I removed a battery holder from a cheap Christmas decoration snowman I had laying around. Finally, I inserted the fixed chip back on the main board again. The computer now remembers both CMOS settings and time, this is necessary for an hard drive to work as to correct type of hard drive needs to be preset from a list.

The “Dallas”-chip for CMOS settings was given a second life with a new battery.

Harddrive: The original 2.5″ Conner harddrive was “dead”, no surprise really. I removed the drive and tested it on an Linux PC with testing software to make sure it was really dead. The computer uses an IDE/PATA harddrive, so a CF memory card adapter should work as a replacement. I installed a CF card and a CF-IDE adapter, it worked perfectly for a few minutes, then it froze. It was not going to work with this adapter or CF card.

Then I got an SD memory card adapter for the IDE/PATA controller instead, I was told this was more compatible with old IDE interfaces. I got an 128 MB SD card laying around. I managed to setup and format an 102 MB partition. To make it autoboot, I had to use the unofficial option “MBR” for the FDISK command, FDISK /MBR. It forces the boot sector i be written on the card, or something like that. Luckily this worked.

The original Conner IDE/PATA 2.5″ hard drive, 63 MB.

Keyboard cable: Keyboard cable cover plastic was in a terrible condition and was cracking and falling off. I found a coiled keyboard extension cable with the old 5 pin DIN connector on eBay. It was very difficult the split the keyboard open without breaking any of the clips, three of them broke even when I used my time on “wrestling” it. Then I had to just measure with my multi-meter what color of wires corresponded to the old cable and solder it onto the keyboard PCB very carefully. It turned out great.

Replaced the old cracking keyboard cable with a new.

Floppy drive: The plastic eject button was missing. I made a 3-D model of the eject-button by looking at photos and measuring. I also first made a wood mock-up to be sure I got it right. It fitted just perfect. When I was at it I also lubricated the moving parts inside to floppy drive.

Made a new eject button, the original button was missing.

Mouse and FPU: As a bonus, I was lucky to find an old serial port mouse for it laying around at my job. I also installed an 80287 @ 8 MHz FPU, just because it was a free socket for it.

My Compaq Portable III running Windows 2.1 and Excel.
Compaq Portable III

Remi Jakobsen


I'm collecting classic computers and video games, stretching from the 70's into the 90's. Restoration, history, usage ...


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4 thoughts on “Compaq Portable III

  1. Thanks for the info. I am waiting for my Compaq Portable to show up and see what needs to be done to make it fully operational!

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