[Coco] Coco 3 high-density floppy controller/IDE interface

[Chuck Youse]

Hi folks,

I recently designed and built some PCBs built around the 82077AA-1 for
the Coco 3 - it's a floppy controller for DD/HD disks (so it supports
your standard 1.44MB 3.5" floppy).  Since I had the room I also threw on
an 8-bit IDE interface (typical waste-half-the-sector design).  

I'm still cranking on the software to verify operation (and that the
Coco can keep up with the 14us data rate) but so far all signs are good.
Ultimately it should work nicely as a high-density, no-halt controller
for OS-9, if the software is properly tweaked - the 82077AA has a
16-byte FIFO that should eliminate the HALT/NMI hack of the Radio Shack
design, if the Coco is running at 1.78MHz.

As it's meant to take the place of a standard RS disk controller, it
also has the 8K EEPROM 28-DIP socket on it for Disk Basic (or whatever).

I personally don't use RS-DOS, so I had no intention of patching Disk
Basic -- my ROM will simply allow automated booting either from floppy
or an attached IDE disk.  Also, I don't really plan on supporting
multiple drives, as there's little need for more than one floppy drive
when you've got a hard disk... but the controller itself actually will
support two drives on an PC-style twisted cable.

Anyway, I've got an extra board or two (and schematics, etc.) if anyone
wants one for development purposes, either to patch Disk Basic or get in
on the no-halt OS-9 driver action.  At some point I may offer them for
sale a la Cloud-9, but I doubt there's really enough interest for that..

C.