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. > > 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. FrankReceived on 2019-01-10 09:02:08
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