Re: Did Commodore cheat with the quad density floppies?

On Tue, Jan 8, 2019 at 5:39 PM Gerrit Heitsch <gerrit@laosinh.s.bawue.de> wrote:
>
> On 1/8/19 5:07 PM, Mike Stein wrote:
> >
> > I think it was a clever hack; if you insist on seeing it as evidence of the incompetence of the designers and engineers who had to build it within the usual constraints, so be it.
>
> It was a clever hack. But it also meant you were limited to only 2
> drives per Controller where the standard back then allowed up to 4
> drives on a cable.

I don't really have a strong opinion on this, but I'd like to have a
better background. How did the various CP/M machines 'solve' this
issue? Did both motors start together or did they have separate cables
for each drive?
I have used a few CP/M systems in the early '80s and some Olivetti
'70s computers with 8" drives always spinning (all of them, I remember
they seemed strange) and of course CBM, Apple II computers and a few
early MS-DOS compatible systems. I remember an NCR computer with 2 x 5
1/4 drives, running a custom version of MS-DOS 1.14 I think. Every
standard newer MS-DOS disk I tried on it, never booted.

I had at one point a linux box (back in the 1990's) with 3 floppy
drives: 5 1/4" HD drives can't really write DD 48 TPI media, in the
sense the saddle (or tunnel) erase head is too narrow and can't
completely erase a previous track written by a proper 48 TPI head,
this isn't an issue if you read the DD disk in another HD drive, but
usually you wanted to read on an older DD drive that would get noise
from the previous-not-completely-erased track data, so I had 2 x 5 1/4
drives, one HD, the other DD and one HD 3 1/2 drive. I ended up using
two floppy controllers for that, even if I remember there was a way to
actually jumper one drive to have three drives on the same controller.
I have nowadays two linux box, one with HD drives, one with DD drive
on it, just in case :)

(I guess this thread's gone too far away).

Frank