Am Mittwoch, 9. Januar 2019, 12:45:05 CET schrieb Gerrit Heitsch: > On 1/9/19 12:08 PM, Francesco Messineo wrote: > > On Wed, Jan 9, 2019 at 12:02 PM <silverdr@wfmh.org.pl> wrote: > >>> On 2019-01-09, at 11:43, Francesco Messineo <francesco.messineo@gmail.com> wrote: > >>>> At least IEC still allows more than two devices ;-) > >>>> > >>>> But no, the IEC on the C64 is another example of CR(ippled) hardware, > >>>> plus VIA-bug workaround ridden implementation. Its big brother GPIB, > >>>> while predating both, wasn't bad though.>>> > >>> Yes it was slow, but I couldn't think about a better compromise, > >>> really. > >> > >> 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. And sure, one of the > > first things that I purchased when I could, was the speeddos mod, > > even if I needed to go back to plain IEC speed whenever I wanted to > > plug the super-fast 300 bps user port modem :) > > From what I read, Commodore had planned to do a rework of the 1541 > using a 6526 (probably like in the 1570/71, or just replacing one 6522 > with a 6526), but someone deleted the necessary traces to use the shift > register from the C64 schematics and when that was found, they already > had a lot of boards produced. So they dropped the rework of the drive > and went with bit banging I/O. And they even had to slow that down > compared to the VIC-20 due to the badlines VIC-II introduced. > > I would really be interested in what would be necessary to get a C64 to > what was initially planned. http://a1bert.kapsi.fi/Dev/burst/ - VICE emulates this, and the C64RMK2 can do it too -- http://hitmen.eu http://ar.pokefinder.org http://vice-emu.sourceforge.net http://magicdisk.untergrund.net Leute, es muss mehr gesoffen werden! <Theodor Heuss>Received on 2019-01-09 13:01:52
Archive generated by hypermail 2.2.0.