I have not backed up the cal parameters yet. I have some 3.5” disks due to arrive today, so I will. I will take a look at that pin too. Would you happen to know if that EEPROM is buffered from the CPU, or does it get written directly?
My plan at the moment is to look at some of the lines (CS, RD, and WR) with my Logic Analyzer. I suspect read is ok, or the instrument would not work whatsoever. I will then try to set those option bits over and over again and see if I can monitor any activity on the three pins above.
Rich