On 06/22/2017 07:36 PM, silverdr@wfmh.org.pl wrote: > >> On 2015-10-13, at 07:48, Gerrit Heitsch <gerrit@laosinh.s.bawue.de> wrote: >> >> At the end of 1986, Commodore changed the process from NMOS to HMOS-II. For a short while, some CIAs were labeled '8521R0' but then they went back to the '6526' label. Usually they were also fast enough for get the 'A' for 2 MHz operation. The HMOS-II-CIA also changed a bit timingwise, that's where the legend originated that the 6526A behaves differently than the 6526. > > They DO behave differently. For example my old test cart shows CIA related failure when using the "6526A". Does it still show that when you use a 6526A-1 made in 1985? I expect not. So the definig characteristic is not the 'A' but the datecode. If the CIA was made at the end of 1986 or later, it's HMOS-II and internally a 8521. Since HMOS-II is faster, they all tested good for 2 MHz and go the 'A' stamped on them. Some of them were even good for 3 MHz and got a 'B'. Do we know how exactly the differ timing-wise? I guess this is related to what Marko wrote yesterday? > It's something about the timer IRQ happening one cycle earlier or later than the NMOS version. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2017-06-22 18:02:41
Archive generated by hypermail 2.2.0.