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The Compaq Portable III was a PC/AT compatible computer released by Compaq Computer Corporation in 1987 for a base price of $3,999. Equipped with an Intel 80286 running at 12MHz, between 640KB and 8MB of RAM, CGA graphics, and a 10” amber gas-plasma display, it was only half the size of previous Compaq portables.
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I acquired this particular Compaq Portable III (CP3) at auction from the Reuseum Collection for $350, untested. Much to my surprise, it came with the relatively rare expansion bay installed. The expansion bay includes 2 ISA expansion slots and is the only way to add ISA expansion boards to the CP3. At the time of purchase, I could not find any expansion bays for the CP3 for sale anywhere online. Finding a CP3 with one already installed was a lucky break. I had always wanted to own a machine with a gas-plasma display and here it was!
The CP3 upon initial inspection seemed to be in good condition, if a bit dirty. The machine did not come with any power cable and the keyboard cable insulation was crumbling, as is a common problem with the CP3. I connected a power cable to the CP3 and turned it on. The power supply fan hummed to life as I joyfully watched the orange gas plasma display warm up and display the initial ROM test. The CP3 displayed two errors:
| Code | Description |
|---|---|
162 |
System Options Not Set |
163 |
Time & Date Not Set |
Both of these errors can be attributed to a dead CMOS battery. I was able to “resume” with the F1 key, indicating that the keyboard had at least some functionality. The machine attempted to boot from drive 1 - a 3.5” disk drive - but the CP3 did not come with any boot media in 3.5” disks. It did come with two Setup & Diagnostic disks in 5.25” disk format.
I was extremely relieved to see that the gas-plasma display was operational.
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Error codes 162 and 163 both point to a dead CMOS battery. Replacing the battery is the first step to getting the machine to boot successfully.
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This particular CP3 came with a Dallas DS1287 real-time clock (RTC) with a non-serviceable battery. Originally, it was thought that when the battery within the DS1287 RTC “went flat” that one would simply replace it with another DS1287 as an entire package. However, 30 years later, this is no longer a viable option. DS1287 RTCs are next to non-existent on the open market (or at least $75) and even if one were to find some sold as “new old stock” the battery would be expired in those as well.
I have seen some restorations where the internal battery in the DS1287 is bypassed by exposing the battery terminals via removing material from the plastic package shell. At that point, a new coin cell battery holder can be hot glued to the top of the shell and new wires soldered onto the new battery terminals. This solution likely wouldn’t work in the CP3 due to how close the rear of the computer’s plastic case is to the DS1287 chip. Any solution that was substantially taller would not allow the case to close.
A better solution in my opinion is a custom PCB called the nwX287 by Necroware. This PCB allows you to replace multiple DS1287 or DS12887 by using a Benchmarq 3285 or 4285 RTC, a crystal oscillator, and a user-serviceable battery! I liked this solution much better as it seemed cleaner and is only 1mm taller than the original DS1287 package. I ordered a small run of 9 of these boards from OSH Park so that they’d be made in the USA. At such a small board size, I was able to order 9 nwX287 boards for only $13.
The dreaded Dallas DS1287. Some CP3s came with a separate user-serviceable battery. Unfortunately, this one did not.
nwX287 by Necroware rev.2 top as ordered at OSH Park.
nwX287 by Necroware rev.2 bottom as ordered at OSH Park.