Weird and Wonderful PCs and PC Mods, Your Stories

Sleepless In Cleveland

From: Will Dudziak

I wish I had a picture... but this is a short story about an 'old school' computer mod.

My grandfather was a PhD physics student back in the 1950s at Case Western Reserve University. He had many friends that did a lot of work on computers back then. It so happened that one of the more dedicated students was having so many problems getting his code to run correctly that he decided to 'camp out' in the computer room until he got it to work.

Often, the run-times for applications were measured in hours. Because my grandfather's friend couldn't monitor the output while he slept, he set up a speaker system to make a sound based on the last few bits of the instruction pointer. Now, normally this meant that the speaker output was fairly random, producing almost white noise. But if the speaker started making a solid tone that awakened him, he knew the program had gotten itself into an infinite loop.

5 MB Hard Drive Connected To Golden Space Helmet

From: weblurker

When you wrote the bit about the SOL-20, I realized that "PC" didn't just mean an 8086 based computer. So I have a story from prehistoric times. Yet the story also touches on something from the modern day.

Way back in the early 1980s, I knew someone in Toronto who owned an electronics store. He often sold surplus equipment. One day I went into his store and saw that he was selling 5 megabyte hard drives connected to a giant 2 foot diameter golden space helmet containing a colour monitor.

I asked about that machine. It turns out a defunct company called "Zap Systems" had tried to make a computer based kiosk system for selling vacations. They had hoped to show videos of exotic destinations. The company failed and everything was sold off.

It turns out they had built an 8080 cpu out of AMD 2900 series bit slice ALUs. The 8080 instruction set was microprogrammed using 2900 microinstructions burned in many PROMs. The cpu boards were S-100 based. As far as I know, they also built their own high resolution colour video card, since none existed at the time.

Why use 2900 bit slice ALUs? Apparently because they ran at 10Mhz, much faster than the 2Mhz 8080. I guess they needed the extra speed to play video clips.

They managed to get CP/M running and wrote their own BIOS to run the hard drive.