Having poked about with two synchronised M5000's I found that the address bus on IC29 was garbage on the bad M5000 and the only way I could remove the garbage was to pull IC18 and IC23 (74LS257) then the address bus was quiet. I checked the two control signals to these ICs nPROC and nS6 and these were identical to the working M5000. The INDEX pulse is almost random It would be good to know what things can create addresses, I think only the BBC via the 1MHz bus and this pair of 74LS257's do, but I'm not 100% sure, anyone know?
Statistics: Posted by maniacminer — Sun Apr 07, 2024 11:52 pm