Re: Differences between Classic ROMs from AMI or MOSTEK ? Message #3 Posted by Bernhard on 25 July 2005, 8:08 a.m., in response to message #2 by Michael F. Coyle
Hi Michael,
"different precharge location" - a very good clue, I'll reexamine both
AMI and MOSTEK CTCs, ARCs and ROMs again on the scope and watch out for
what happens around the clock pulses. Maybe it's a combined effect in
the chip set, like in the Woodstocks, where I also had some initital difficulty to operate ROMs without the ACT.
One odd observation, though: the stubborn Mostek ROM I have got is from a fully functional HP55 which has the following strange mix of ICs:
Mostek: RAMs and the 1818-0120 ROM (page 0...3)
AMI: CTC, ARC and the two other ROMs
I also have a HP45 with all-AMI chipset except for the Mostek ARC.
Both machines are 1975 vintage. Maybe the progress in process technology since 1973 has helped to relax the timing issue so HP was able to start mixing chips from different manufacturers, but a small difference was left - which is not properly implemented in my current ROM reader hardware. AMI ROMs read perfectly, though.
best regards,
Bernhard
|