On 03/05/2015 09:31 PM, Martin Hoffmann-Vetter wrote: >> Remember, Commodore made a lot of different chips just because they >> could... > > ...and need it. > >> Why a special CPU for the 264 series and the C128 instead of >> just using a different bond out of the 6510? The 8500 is the 6510 in >> HMOS-II > > At this time, CSG build many chips in HMOS. So if Commodore need a huge package of CPUs, they build a new version in HMOS. This isn't a special CPU, it's a variant of an existing CPU in HMOS. Well, the 7501/8501 ist a redesign from the 6510, it really lacks Bit 5 of the I/O-port where the 6510 has all 8 Bits with only 6 of them bonded out. So it should have been possible to use it for the 264 as well, with just different bonding. >> Or why the 6523 and later the 6525 (6523 with IRQs)? And >> then all the 77xx-TTL replacements... Or the 6529... > > They need these chips. First they can buy it from an other manufactor. In any case, these chips are not available, so they build it self. What's the alternative for a 6529? It's a simple chip, so they designed it, build it und use it. The way the 6529 is used in the 264 series is (from the code I know) write-only. So a simple 74LS374 should be able to do that job. Or, with the keyboard latch in TED what it is, you could have even gotten away with a 74LS244. Might have been a bit difficult to pass FCC though since you then have the buffered data bus on the keyboard matrix all the time. It becomes a different issue when you need full I/O, but that came later when they used the 6529 also in the plus/4 for the user port. Of course there are upsides of having a chip plant 2 doors down as well... After all, that's how we got VIC and SID. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2015-03-06 18:00:05
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