CPM was Re: MDOS (Motorola EXORciser) disk format ?

On Sun, 2003-11-02 at 14:54, Fred Cisin wrote: 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.