On 09/24/2011 04:28 PM, Nicolas Welte wrote: > Segher Boessenkool wrote: >>> The interesting question is... Does the 8521 behave like a 6526 or >>> like a 6526A? >> >> >> 6526A means a 6526 that runs at 2MHz. It has nothing to do with >> die revision. There seems to be a strong correlation though, most >> later chips were 2MHz and most older were not. > > Yes this is very unfortunate. The scene seems to refer to the different > timing versions with the A suffix, while in reality it is the speed > grade. I found the change came in late 1986, the earliest "new" version > I have has a date code of late 1986. This also matches with the arrival > of the reportedly incompatible C128DCR and Aldi-C64 versions. This also matches the appearance of the 8521 in late 1986. Could it be that the change in timer behaviour is due to a mask change done while transfering the 6526 from NMOS to HMOS-II? I wouldn't put it beyond Commodore to just drop the '8521' marking after a short time and just mark them '6526' again. The 'A' (2MHz) would then be a sideeffect of HMOS-II allowing higher speeds. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2011-09-24 16:00:04
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