View Single Post
Old 3rd Jul 2019, 10:47 pm   #132
NealCrook
Tetrode
 
Join Date: May 2019
Location: Reading, Berkshire, UK.
Posts: 51
Default Re: Gemini 80-Bus System

Well, it's progress and good news to know that the CPU can execute code and loop. Odd that the power-on-reset circuit does not work. As John Hanson suggested, maybe that capacitor C44 is leaky. If you are in a card rack with the rest of the working system you should also be able to do a reset by an I/O read or write to port 0xB3 (that would also be a way to do some kind of a test on the ?IC36? decode PROM.

While watching The Cure at Glastonbury (on TV..) I made more progress on the disassembly; it's a nice puzzle a bit like a crossword. I found the jump tables that search a list of escape codes and invoke a code fragment as a result, and I made a bit more sense of some other parts of the code. I'll post the result once I've checked that it assembles back to an identical binary.

Neal.
NealCrook is offline