CompuPro floppy controller differences

Dave Dunfield dave06a at
Fri Sep 8 22:35:38 CDT 2006

>             Is there any practical difference between the CompuPro Disk 1
> and Disk 1A that would prevent a 1A disk from working on a 1? I have a line
> on a Disk 1 controller but only have access to 1A disks from Dave Dunfield.

I have a Disk-1A up and running in my Compupro box - unfortunately I do not
have a Disk-1 to test with. I do however have manuals for both controllers.

>From what I can tell on a cursory readthrough - the Disk-1 and the Disk-1A
are very similar, but not identical:

 - The Disk-1A appears to have some functions available in the write side
   of some registers which were read-only on the Disk-1 - these seem to
   control features that had to be set by switches or board modifications on
   the Disk-1.

- The Disk-1 has a bit-bang serial port which has been dropped on the 1A.

- The difference is NOT the difference between a 765 and a 765A - both
  manuals list the 765A as the NEC FDC.

- The 765 and motor control registers appear to be in the same place on
  both controllers.

I have a set of original Cromemco CP/M diskettes, and the labels do NOT
mention anything about a specific floppy controller board - my guess is that
the disks would boot and run on either controller. (But as noted above, I
cannot confirm this, so it is just a guess).


dave06a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Collector of vintage computing equipment:

More information about the cctech mailing list