Am 10. Januar 2019 09:01:10 schrieb Francesco Messineo <francesco.messineo@gmail.com>: > On Thu, Jan 10, 2019 at 8:26 AM André Fachat <afachat@gmx.de> wrote: >> >> >> >> Am 10. Januar 2019 08:20:16 schrieb groepaz@gmx.net: >> >>> Am Donnerstag, 10. Januar 2019, 08:11:04 CET schrieb André Fachat: >>>> Am 9. Januar 2019 12:17:17 schrieb Francesco Messineo >>>> >>>> <francesco.messineo@gmail.com>: >>>>>> The major issue was actually the speed - not really of the bus but of the >>>>>> 1541 implementation with 6522 software workarounds making the bus look >>>>>> worse than it really was. Common thing was to add at least the parallel >>>>>> connection to 1541, bringing it somewhat closer to the original GPIB. And >>>>>> yes - it still allowed more than two devices and obviously not only the >>>>>> floppy drives. >>>>> >>>>> Yes, that was due to a bug in the 6522 chip. >>>> >>>> Never having fixed the shift register bug in the VIA 6522 e.g. in a new >>>> revision is my biggest gripe with MOS and Commodore. It would have made so >>>> many things so much easier. >>>> >>>> Well, that's history. Anyone know if there is a fixed CPLD/FPGA VIA? >>> >>> the CMOS versions (which are still available) have the external clocking bug >>> fixed, AFAIK >> >> Did they? Do you get them still? > > 65C22 can be still purchased new, I believe mouser has them. I don't > know if the 65C22 has that bug fixed, but all it takes to fix the bug > is a 74LS74 in front of the VIA (I remember checking this many years > ago, si I might be wrong), so it's not such a "big" problem if one > wants to use the old 6522. I know this solution, but IIRC this prevents bidirectional operation without extra direction control. > >> >> After sending I remembered the WDC but they are not plugin replacements as >> they have active IRQ drivers and need an extra diode. > > well, little extra components aren't that bad anyway, if one really > wants to use the shift register. Yes but makes it less easy for unexperienced users. André >Received on 2019-01-10 10:00:30
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