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

[Gene Heskett]

On Thursday 03 July 2008, David Hazelton wrote:
>AS my Floppy controller has been dead for a few years, I'm interested in
>the final product.  I could test it out, but since I haven't had my coco
>running for a few years, due to my B&B controller needed a floppy boot
>to load OS9.  I'm not sure I can debug any of it.
>
>David Hazelton

I too might be interested in it.  I have a Disto SC-II no-halt now, but the 
no-halt driver cannot format a floppy without crashing.

>Chuck Youse wrote:
>> 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.

What does it do with the 3rd ds line?  That was not normally the fdc's 
responsibility, but was selected via separate latching buffers on the 
controller pcb.  There were times I had considered replacing the 3 DS lines by 
feeding them to a 3x8 decoder to get 8 drives & then I wouldn't be moving drive 
cables all the time to switch from the various flavors of 5.25" drives to the 
3.5".

>> 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..

How much?

>> C.
>>
>>
>>
>>
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-- 
Cheers, Gene
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