There seems to be a lot of discussions regarding
handling old / odd
floppy disk formats. What Fred said above is a truth with severe
limitations. It is my experience, that modern floppy controllers, and
_especially_ those embedded on motherboards, will
not read anything other then 3.5" disks (720K, 1.44M and 2.88M) and
5.25" (360K, 1.2M).
The older formats, like 5.25" 320K, not to speak of 160K are not
I am wonderign how on earth you can make a disk controller (note, not the
OS driver software, the physocal controller) that works correctly with a
9-sector-per-track format, but fails with the 8 sector-per-track version,
all other parameters being the same. Because that's the only difference
between the 320K and 360K MS-DOS formats.
Similarly, I can't understand how you can make a controller that works
correcty with a DS disk but fails with the SS version.
supported, or should I say are not supported on the
systems I've
delivered for the last 8-10 years.
Please note that I only take MS-DOs formats in consideration. Anything
other, like CP/M or 8" disks, is totally out.
Err, considering that the 8" drive and the 1.2M 5.25" drive are very
similar at the hardware interface level, it would be difficult to make a
contorller that worked with one but which fails with the other.
And some CP/M formats are pnysically almost identical to the standard
320K MS-DOS format. Hardware that can read one can also read the other.
There was a mention of MicroSolutions UniForm software. The software
(at least the version I had) was able to read (some) CP/M formats by
doing nasty things to the parameters in the floppy controller. When I
tried it again some years ago, it was a total flop, probably because of
the limitations as described above.
The main problem is that many PC disk controllers (going back to the
original IBM card in the PC and PC/XT -- check the schematics) can't
handle single density (FM) recording correctly.
scrapheap just for this purpose. Or maybe even a
museum piece: the IBM
AT. In other words : the older the better.
I happen to be typing this on a much-hacked PC/AT (orignal IBM, original
motherboard with my own hardware mods, etc). Still works fine, and I have
no intention of downgrading to a more modern machine.
-tony