The Retro Challenge is a one-month long excuse to do cool stuff with old computers and blog about it (vaguely wrapped up as a competition).
(This year the challenge is being hosted by Mark Sherman at http://mwsherman.com/RCR/2020/04/. I started my challenge on 1 April without knowing for sure if it would be running this month. but I wanted to do it anyway!)
In 2018 I tried to restore two Osborne 1 portable computers. One restoration was completely successful, but with the other I couldn’t narrow down the problem in the disk controller as I lacked sufficient test equipment.
I now have an Oscilloscope and a Logic Analyser so hope to be able to complete the repairs.
My updates will appear here:
- Day 1: I eliminated the Double Density board as the source of the problem: Twitter link
- Day 2: I used the oscilloscope to prove that the floppy controller is talking to the floppy drive (probably correctly, although I’m not yet sure): Twitter link
- Day 3: I connected up a Logic Analyser to the floppy controller and started to look at its communication to the Z80 CPU: Twitter link
- Day 4: I copied some LA signals to my desktop computer, and have started learning how to write a protocol decoder: Twitter link
- Day 5: I looked into the exact timings listed in the floppy controller datasheet in preparation to writing a protocol decoder. However the logic analyser data doesn’t match! Smoking gun? Too early to say. Twitter link