Re: Did Commodore cheat with the quad density floppies?

From: groepaz_at_gmx.net
Date: Wed, 09 Jan 2019 12:49:03 +0100
Message-ID: <1697037.8FyrlEIdSr@rakete>
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

-- 

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Leute, es muss mehr gesoffen werden! 
<Theodor Heuss>
Received on 2019-01-09 13:01:52

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