The IBM PS/2 series of computers is a true classic in the computer history. Not so common as a home computer but often seen in office spaces in the late 80’s and the 90’s. The Model 30 released in 1987 features an Intel 8086 processor running at 8 MHz. A year later, an upgraded version featuring an 80286 processor was released. The 286 version of the Model 30 was one of my very first PCs, and I really like the clunky, boxy design!
I recently found a Model 30 (the 8086 version) on eBay, with just a few issues, and thought it would be an interesting project to make it work and see what potential upgrades I could do. IBM is known for their non-standard parts and most models in the PS/2 series use the proprietary Micro Channel Architecture (MCA) bus. The Model 30, however, is one of the few models that use the ISA bus standard commonly found in PC compatibles. This means I should be able to use non-IBM expansion cards for sound and network. The 8086 version of the Model 30 only supports 8-bit cards though, so there are quite some limitations still (the 286 model supports 16-bit cards).
The default video output is MCGA (Multi-Color Graphics Array), which was only ever used on the early PS/2 models. It supports all CGA graphic modes plus 640x480 monochrome, and 320x200 with 256 colors. No standalone MCGA graphics cards were ever produced, and the standard was quickly replaced by the superior VGA standard in later models. Luckily, it uses the same 15-pin connector as the VGA standard, and most VGA monitors should work just fine. I had to find a slightly older VGA cable though, since the MCGA standard actually only uses 14 pins, and a 15 pin cable doesn’t fit the connector on the back of the PS/2.
Starting up the machine
The power switch design is actually pretty interesting. The front switch is connected to the back of the machine with a lever that in turn flips a switch on the power supply. Clever! Maybe… I hope I don’t have to fix the power supply later, since it seems sealed without any screws.
The computer has 128 kB onboard memory, and supports up to two additional 256 kB memory modules, giving a total of 640 kB when maxed out. The memory modules are 30-pin SIMMs, but, of course, it’s not standard modules but slightly different. So you have to get proper IBM memory. Luckily I found two modules on eBay, and they installed just fine.
The computer starts up, but displays two error messages:
- 161-Set Date and Time
- 1790-Fixed Disk Error
The date and time issue is expected as the battery is probably dead. The fixed disk error might indicate that the hard drive is not working, which is also kind of expected. I’m not too worried about these errors for now.
Since the hard drive is obviously not working, I have to boot from a 720 kB floppy disk. I haven’t had a floppy drive for a long time so this might present a problem. I bought a USB floppy drive, but it doesn’t seem to work with my Mac, so I’ll have to get back to this problem.
So the computer seems to be working, but it needs some cleaning. The battery issue is not important at this stage, but I might have to find a replacement later. In addition, I have the following ideas for this machine:
- Swap the 8086 processor with a replacement NEC V30 - The NEC V30 is a pin-compatible drop-in replacement for the 8086 processor. It’s supposedly faster, and includes some 80286 instructions. The real value of doing this upgrade apart from showing nice numbers in benchmarks is questioned though.
- Add an 8087 math co-processor
- Add a network card
- Add an XT-IDE CompactFlash controller
- Add a Sound Blaster sound card - The sound card I have is 16-bit, but it’s supposed to work fine in an 8-bit bus as well. The 16-bit bus is only used for CD audio from what I’ve heard.