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IBM PS/2 - Steady Progress

Written by Stephen
October 16, 2018

First things first - I have sourced a CRT! It was delivered for free and works great. Since the PS/2 System 50 has a weird VGA port, which was common in this time period, I had to break a pin off the monitor cable.

Even though the plastic colours do not match, I prefer it greatly over the LCD I used before.

I also received a USB floppy drive in the mail. I tried both MS-DOS and an IBM initialization disk image I found, but it kept dropping me into BASIC. After more troubleshooting, it turns out the floppy drive in the unit is broken. It's a common problem, and should be fixable by replacing its capacitors. When trying to get the drive apart, however, I found out that a few of the screws were completely stuck, and made out of a very soft metal which couldn't handle my screwdriver. I will probably have to drill them out and find replacements.

When troubleshooting, I took the HDD out of the computer, and it no longer booted into BASIC. So, it seems that the BASIC interpreter is stored on the disk, not on the ROM like I previously thought. It turns out it's only 20MB, not 40.

I looked into the development of an MCA card. As far as I can tell, it's not been done before by a hobbyist. I was able to find 2 PDFs on the physical specifications of MCA cards, as well as how the protocol operates. It seems like it would be quite easy to design a card. For me, the hard part is designing the edge connector - the physical specifications are hard to read and contain ambiguity. There's already an MCA card in there, which I may have to measure. I'd like to make an eagle library with the connector, and then I can develop as many boards as I want. In the beginning October 11, 2018

An IBM PS/2 model 50 computer showed up on Kijiji about a week ago and I knew I had to have it. For only 20 Canadian rupees, I got a 286-based machine with one megabyte of RAM. Its 40MB hard drive was blank, and I do not have a floppy drive, so I can't create a 16 bit boot disk.

Surprisingly, though, it still boots - there is a BASIC interpreter stored on ROM. I never learned BASIC, but the language was intuitive, and I only used a minimal amount of documentation. I manually retyped a mandelbrot generator I found on github, which worked perfectly! Unfortunately, the built in interpreter only supports 4 colours - which I configured wrong, resulting in a monochrome program output - and I only allowed it to run for about 3 hours.

I also wrote my own BASIC program to generate Serpinski Triangles. This only took a handful of code, and was surprisingly quick, generating a recognizable image in a few seconds! The below image was generated in about a minute.

I have a lot of work to do. I am working on sourcing a CRT monitor, to make the experience more authentic, and I will have to get a PS/2 keyboard from home, as I am borrowing one from a professor. I have one at home, but did not bring it to university with me. I would also like to build my own MCA card, although I'm not sure what for(maybe ethernet), and solid state drive. I may end up porting SteveOS to 16 bit, or create a new OS entirely. At the very least, I would like to get something DOS based for the short term. A dot matrix printer would also help complete the system!

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