[Coco] Four floppy drives?

[Arthur Flexser]

It is puzzling how you managed to get 4 double-sided drives working.
Ordinarily, only 3 would be available.  You have 4 drive select lines, but
one would normally be used as a side select for double-sided drives.  I
vaguely recall an article that described some scheme that recognized that
when two drive select lines were simultaneously selected, a fourth drive
would be accessed.  Did you do something like that?  Did you modify the
Disk Basic ROM?

Art

On Fri, Jul 31, 2015 at 2:52 PM, David Gettle <david17361 at gmail.com> wrote:

> When I was in college I was running 2 5.25 and 2 3.5" DSDD floppy drives
> off a FD502 card from Radioshack with no problems, all I had to do was set
> the drive jumpers and have a custom cable made. amazing that the CoCo would
> allow me to format all of them at the same time in OS-9. I Ticked off some
> UNIX users because their unix boxes couldn't do that :)
>
> On Tue, Jul 28, 2015 at 10:15 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
>
> >
> > > On Jul 28, 2015, at 22:13 , Chris Osborn <fozztexx at fozztexx.com>
> wrote:
> > >
> > > III supported four drives, two internal and two external, but they were
> > on separate buses so it only had to select between two drives on each
> > ribbon.
> >
> > Aha! I recently had reason to study the floppy signaling in the
> > II/12/16/6000, and they also separated the drives into internal and
> > external busses with separate buffering and MUXing.
> >
> >
> > --
> > Mark J. Blair, NF6X <nf6x at nf6x.net>
> > http://www.nf6x.net/
> >
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco
> >
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> https://pairlist5.pair.net/mailman/listinfo/coco
>