• 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.
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 ...

Post navigation

18 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!

  2. Nice Job on this lugable, how did you get the setup floppy made?
    I’ve been trying for a while on mine and the exe made floppy wont boot
    you wouldn’t have the files in the disk I can toss on a dos 1.44 floppy?

    1. Thanks. You can boot with any 5.25″ HD 1.2 MB or DD 500 KB MSDOS (or MS Compaq DOS) boot disk. As you probably already know, you make an MSDOS boot disk by using the “SYS” command or by runing the SYS command by adding it to the FORMAT command parameter, like this: “format A: /S”. I can send you the Compaq setup program or disk image files for Compaq DOS.

    1. If I remember correctly, on mine, it was clipped together, must be very careful, take your time and not break them. But I think there is another variation with “hidden” screws instead of clips, maybe hidden between some of the key caps, so you have to maybe remove a couple of key caps to get to those.

  3. Ok thanks good to know. Not sure if you’ve come across this issue, but the screen on mine has several black lines going vertically. Is this something that can be repaired, or can this be written of as a failed screen.

  4. I don’t know. It’s a gas plasma screen. I repaired a Macintosh Portable with LCD screen with stripes. The missing stripes was caused by broken wires in the monitor flat cable going to the main board, maybe you should measure the connectivity in the cables to the display panel. (BTW: as you probably know you can connect an external cga/rgb monitor and use a hot-key to switch to that screen).

      1. Whatever is fair – not looking to make anything on it… just want it to go to a good home. 🙂 I’m going through gear and cleaning house. Let me see what else I have and I’ll shoot you some pics. thx

  5. This is fantastic! I just picked up one of these and want to get it restored. Right now I’m getting a 201 memory error.
    Mine does not have the Dallas “RTC” chip I have the M146818P chip. Would I still need to change that out for a battery? Thanks!!

    1. I don’t know that chip, if the battery sits in that chip you need to replace it somehow I think. However you should be able to boot from a floppy even with dead battery and the default CMOS settings. If you got a memory error message, maybe there is a failed RAM chip on the motherboard that needs to be replaced, I would have started with that.

  6. Please, can you tell the output voltages values for te power supply’s connectors? The 12 pin and the molex. Please, i can’t found the information anymhere!!

Leave a Reply to Peter Haggarty Cancel reply

Your email address will not be published. Required fields are marked *