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

11 Sep 2006

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Subject: RE: CompuPro floppy controller differences
   From: "Chuck Guzis" <cclist at sydex.com>
   Date: Sun, 10 Sep 2006 16:37:41 -0700
     To: cctalk at classiccmp.org

On 9/10/2006 at 3:53 PM Allison wrote:

  CCS did
have some 5.25" disk formats (both 48tpi and 96tpi) supported.
I have no idea whether they ever used them as boot disks. 
I'd have to read the boot rom source.  Who knows it's been years since 
I read the FDC manual so it could be wired in, the controller does 
do 5.25.   I'd bet a penny there is no reason why not.   
Must be possible as my notes say all 5.25" formatsl reserved 6 cylinders*2
sides for the boot tracks.  On the 512 and 1024 bytes-per-sector versions,
that's about 60K.  On the 256 byte/sector version its about 55K for the
boot.     
CP/M boot image is CCP (2k), Bdos(3.5k) and bios (.5k->3.5k), assuming a
large bios the whole show is 9k.  IF we add the two secondary boot sectors
(assume 128byte sectors) to that it's 9.25k. Likely, even that is oversized.
Standard SSSD 8" is two tracks reserved for boot(6656bytes!).

Looked at the manual, the boot is generic enough that it grabs the first 
two sectors and jumps to that code.  Sequence is Rom boot, seconday boot
using the rom read/write routines and the seconday boot loads the whole
show.  That code is CCBOOT.  The CP/M image once loaded jumps to BIOS 
Coldboot and that initializes everything and starts the show.

The manual says two tracks on 8" and 3 tracks on 5.25 with track 00 being 
128 byte single density only.  NOTE the manual says tracks not cylinders.

FYI: the standard rom has a MOSS monitor (console is 8250 at 40h) and 
also carries read write primitives and boot.  If you had a board with 
8250 serial on it that could be configured for address 40h that board
would be easier to boot on a system without a boot disk in hand.

Allison