CompuPro floppy controller differences - test-drb@ccmp.vtda.org

9 Sep 2006

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Subject: Re: CompuPro floppy controller differences
   From: "Dave Dunfield" <dave06a at dunfield.com>
   Date: Fri, 08 Sep 2006 22:35:38 -0500
     To: <cctalk at classiccmp.org>

              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).

Dave 
You missed one item, different eprom and contents.  The differences there
include boot code for 8088 and in very late 1A version 68000. They are 
essentially the same, though of the two the latter 1a is prefered.  

Allison