Category Archives: RetroChallenge

As part of my RC2012WW project, I ran an 8080 exerciser and other instruction test programs on a Sol20 to better understand the behavior of the 8080′s flags (which are NOT exactly the same as those of the Z-80), and … Continue reading →

By writing some additional 8080 test programs, running them on both the Sol-20 and my simulator, and comparing the output, I’ve found and fixed several bugs in my simulator.  Now the 8080 Exerciser running on the simulator matches all the … Continue reading →

With a good power supply filter capacitor, the Sol-20 is now running sufficiently reliably that it passed the 8080 Exerciser., generating the expected CRC values. In order to find the bug(s) in the 8080 simulator I wrote last month, I’ve … Continue reading →

The reason the Sol I’ve been using is unreliable (mostly in the first 30 seconds after powerup, but sometimes later also) is that C8, a 18000 uF 10V electrolytic filter capacitor for the 5V power supply, has gone high-leakage. It’s … Continue reading →

Frank Cringle released a GPL’d Z80 CPU exerciser in 1994, and Ian Bartholomew released modified versions for the 8080 and 8085 in 2009.  Since I don’t have CP/M running on my Sol-20 yet, I’ve modified the sources to assemble with … Continue reading →

I got a monochrome monitor out of storage, and unsurprisingly, it shows the Sol-20 video much more clearly than the color TV did. I hooked up the serial port of the Sol-20 to a null modem adapter and USB-to-serial adapter … Continue reading →

I’ve now got one of the four keyboards fixed. Actually I probably have mixed parts of one keyboard with another. I’ll have to make or buy more foam pads for the other three. Two of the keyboards had foam pads … Continue reading →

I’ve continued work on my KC/CUTS tape decoder program. The decoder works well with clean audio files, but not so well with noisy ones. I’m not completely convinced that using the Goertzel algorithm has been a good idea; possibly just … Continue reading →