1551! Re: 9V AC needed for C64? (C128 and serial bus q)

From: Richard Atkinson (rga24_at_hermes.cam.ac.uk)
Date: 1998-09-06 15:24:19

On Fri, 4 Sep 1998, Ruud Baltissen wrote:

> Hallo Richard,
> > Ruud: Your CP/M cartridge arrived today. Great job! Must return the favour
> > somehow. Any old 8bit hardware you're looking for? (note: might be rare in
> > the Netherlands, but common in England?)
> Still sorry for the real big delay but illness, tooooo much of work and 
> hollidays delayed the shipping. 
> My second computer was a ZX81. Through this one I got news of the existence of 
> the ZX80. If you can find that one for me, please. But only if it is not to 
> much trouble.

Wow. You don't waste any time :-) ZX80s are incredibly, ridiculously,
utterly, hopelessly, ludicrously rare. Needless to say, I have one (but it
doesn't work). Anything else?

> The CP/M disks on FUNET work fine with this module. But if you have to reset 
> for one or another reason, turn the C64 OFF!!! If you use a reset-button, it 
> seems that something stays resident and the system won't start again.

Probably sets up a cartridge start routine. Anyone else know about this?

> > Quick question: what's the maximum number of Commodore computers that can
> > be on the IEC bus? I'm using the serial bus as a way of networking C64s
> > but since each one has a pullup resistor on the serial bus bits, the line
> > drivers (7406 open collector hex invertors) will only be able to support a
> > few, much less than disk drives. Can I get away with 6 or 8 machines?
> Carefully cut the wire on the top of the resistor. If you need that specific 
> C64 as solo-machine again, a drop of solder will connect the ends again.

Argh! Butchery of sacred Commodore machines! Well okay, so it's only a
C64, but even so... I suppose I have to look up the specs on 7406. I
always thought open collector devices could sink quite a lot of current,
but just how much remains to be seen.

Alright guys, down to business. Guess who found a 1551 disk drive
yesterday? :-) That's right, in its original box with manual and
diskettes. So far I have been unimpressed by its so-called "speed", but
perhaps that's because I'm used to 1541 fastload routines such as Datel's
Action Replay.

So, the question is: how fast can the 1551 be driven? I had a brief look
inside the drive (hmm, quite similar to the 1541C board) and the interface
cartridge, and I can tell you that there are 16 (sixteen!) wires between
the cartridge and the drive. So what are those mysterious coloured wires,
and how can they help us? I figure it ought to be possible to get proper 8
bit parallel transfers, rather than the standard 3 bit (why?!?) protocol.


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