> On 2018-06-12, at 17:05, Mia Magnusson <mia@plea.se> wrote: > >> _Almost_ drop-in replacement, yes. But the die photos are really easy >> to tell apart (an 8521 does not say "6526" on the die, it says >> "8521"). > > I can't remember which versions, but at least some version of the CIAs > can only be used as one of the two CIA's in a C64. Using it as the > other CIA causes keyboard problems. No, it doesn't... > And when using it as the CIA that > generally works causes interrupt failure in the common diagnostic cart > (the one that's not called dead test, not sure if it has a better name > than diagnostic). It's called "Diagnose" and was distributed once by "Roßmöller" > I guess it has cmos drivers instead of nmos drivers > on it's output stage, and that causes problems with the keyboard when > pressing more than one key at a time. The only problem I've come to know about is the above mentioned diagnostic tool, which hasn't been updated to recognise the "off by one cycle" interrupt of the 8521 labeled as 6526A. Theoretically there might be other software that relies on precise IRQ timing coming off the CIA but I don't recall having heard of any. -- SD! - http://e4aws.silverdr.com/Received on 2018-06-14 00:00:04
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