On 06/10/2018 10:50 PM, Segher Boessenkool wrote: > On Sun, Jun 10, 2018 at 10:17:17PM +0200, Gerrit Heitsch wrote: >> On 06/10/2018 09:46 PM, Segher Boessenkool wrote: >>> On Sun, Jun 10, 2018 at 06:42:02PM +0200, Gerrit Heitsch wrote: >>>> On 06/10/2018 05:36 PM, Segher Boessenkool wrote: >>>>> http://siliconpr0n.org/map/mos/6526/mz_mit20x/ >>>>> >>>>> The ports are the low half of the pins (PA on the left, PB on the right). >>>>> >>>>> (I have a .xcf if anyone is interested, marked quite a few signals, but >>>>> I haven't done the port stuff very much. It's about 400MB). >>>> >>>> That looks quite different from the one I posted. Looks like MOS did >>>> quite a bit of redesign between the NMOS 6526 and the HMOS 8521 (which >>>> still got labeled 6526). Might explain the little differences in the way >>>> they behave. >>> >>> No, this is an actual 6526r4. This is an 8521r1: >>> >>> http://oms.wmhost.com/misc/MOS_6526A_CIA.jpg >>> >>> (and this is an 8520r4, the CIA used in amigas; it has a different TOD >>> clock, and as you can see it's different from 8521 in other ways, too. >>> But clearly 8520 and 8521 are more related. The lineage is almost >>> certainly 6526 -> 8520 -> 8521: >>> >>> http://siliconpr0n.org/map/mos/8520/mz_mit20x/ ). >> >> Yes, but the 8521 is a drop in replacement for the 6526 (I have a C64 >> Board with a 8521R0 on U2) and later revisions of that chip have been >> labeled as '6526' again, probably to avoid confusing the customers. You >> can tell them apart by the datecode or by the '206A' or '216A' next to >> the datecode. > > _Almost_ drop-in replacement, yes. Well, yes, one of the timer IRQ timings is off by one cycle. But the die photos are really easy > to tell apart (an 8521 does not say "6526" on the die, it says "8521"). That's why I said that MOS did quite a bit of changes when they migrated the CIA design from NMOS to HMOS. GerritReceived on 2018-06-11 00:00:06
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