Imaging TRS-80/III single-sided disks
cisin at xenosoft.com
Thu Jun 25 19:19:08 CDT 2015
A few more gotchas to be aware of:
Some of the operating systems on TRS-80 started the sector numbering at 0.
Therefore, depending on which operating systems were used, you could have
sectors numbered 0 - 17 , or 1 - 18. That can be confusing if your PC
can't read the first sector, but tells you that it successfully read
Model 1 TRS-DOS is SINGLE DENSITY. IMD can handle that IFF the FDC in
your PC is one of the ones that supports FM/SD. NOTE: some/many? TRS-80
users installed additional hardware for double density, but the OS might
still require FM/SD for track 0. Disks written on a stock model 3 for
use in a model 1 are not quite the same format as model 1 disks.
Model 1 TRS-DOS uses some "NON-STANDARD" DAMs (Data Address Marks). I
don't know how to read those with PC FDC. But, they can be read with
Catweasel, OptionBoard, or other "flux transition" boards.
Or design and build a PC FDC board with a 1771 WD FDC and a WD 179x FDC
just to be able to handle disks with NEC/WD incompatabilities - NOTE: that
disk controller should ALSO have an NEC FDC, or you won't be able to have
full PC compatability.
Model 1 TRS-80 has 35 tracks. They started off using the Shugart SA-400
floppy drive, which is 35 track. I think that most/all? of their later
drives could do a full 40 tracks, BUT don't count on the software
supporting that. Expect 35 tracks for TRS-DOS, although most/all? of the
after-market operating systems supported 40 track, and some supported
double sided drives ("Gee, didn't expect THAT!"), and some users even used
80 cylinder drives, for 720K capacity. Yes, there were also hardware mods
for TRS-80 to use 8" disks. Yes, you can put 3", 3.25", or 3.5" drives on
Not all TRS-80 diskettes were of the highest quality. Be prepared to
clean the heads of your drive after you finish, and maybe periodically
part way through. Some TRS-80 users considered Wabash to be "premium"
Grumpy Ol' Fred cisin at xenosoft.com
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