MDOS (Motorola EXORciser) disk format ?

From: Tom Jennings <tomj_at_wps.com>
Date: Mon Nov 3 14:22:45 2003

On Sun, 2003-11-02 at 14:54, Fred Cisin wrote:
> > A friend of mine has a pile (55) 8" floppies which were created
> > on a Motorola EXORciser MDOS system. Does anyone know if the data
> > on these disks can be recovered on a CPM system or similar, or will
> > he need to find an EXORciser?

CP/M, since it's so close to the iron anyways, is probably a good way to
do a sector dump of the disk. Copy it to a modern machine and
post-process the data.

Getting the sector data off is the task. If it's hard-sectored, you're
probably screwed. (Turn the diskette inside it's sleeve; there should
only be one (a pair?) of index holes. If you see 12 or so holes it's
hard-sectored. Not many 8" diskettes were hard sectored.)

There were two flavors of floppy controller chip in the 70's and 80's,
th Western Digital chips and the NEC 765. I always preferred the WD
chips (1791? 1793? I forget!) They were the best for diskette hacking.
They would read any damn old FM or MFM signal, and you could dump to
memory and do the bit extraction in software. Very cool. The NEC765,
though nominally easier to do certain things, was a lot less flexible
and far more fussy about format.

(I used to run my 86DOS 0.86/MSDOS1.25/MSDOS2.00 system on DSDD 8"
floppies with 9 1K sectors per track. I thought I was very cool for
doing this (cringe)).

The short of it is, if you have a CP/M system with a WD controller, you
can write nice dumb code to do a 'track dump' if you have enough memory
or a sector dump if you don't and see what's electrically on the
diskette.

I wish I had all my old data. I used to pore over floppy track dumps and
could read the MFM header (it's easy) to determine all sorts of stuff.
It's not mysterious, just obscure.
Received on Mon Nov 03 2003 - 14:22:45 GMT