At 18:29 14.08.2005 -0800, Jaap van Ganswijk wrote:
Don't confuse the real floppy controller chip and the software.
The chips still can read FM disks and by the way, MFM and FM
(or DD and SD) use the same medium, but use it in a smarter
manner.
(And building FM into an MFM controller costs almost nothing,
so they do it in the spirit of that every new PC has to be
completely downwards compatible with every old PC.
Unfortunately, this doesn't seem to be true for the VIA chipset of my
computer. I do have software that tries to read FM, but it was not
successful with these disks. Worked fine for many MFM formats where the
bitrate was standard, but not with these disks.
3.5 inch disks are logically identical to 5.25 inch
disks.
Not exactly - the rotation speeds are different, but this VME computer
doesn't see that at all, because the floppy drive has a built-in controller
(comparable to the LS-120 super floppy for ATAPI).
>Thanks for your other hints - I have also seen quite a few filesystems
before, but never really tried to hack one. One way or another, I managed
to get hold of a documentation, so I had the positions for sector
pointers, directory entries and so on.
So what is the remaining problem?
Sorry, there's a misunderstanding: I've had documentation for all the other
filesystems I've been working with, but I don't have documentation about
VERSAdos. I've passed along Uwe's link (thanks for that!), hoping that it's
really related to CP/M (which is not the case, according to your answer).
Should you have some kind of documentation for any Motorola filesystem, any
hint is very welcome.
BTW. I never wrote a 68000 emulator, because it has a very
chaotical instruction set and it was 32-bits and I was still
writing the emulators on an 8/16 bits system.
There are nice 68K emulators out there, the most interesting being in the
Amiga emulators: It's a JIT compiler, beating any real 68K processor. A few
years ago, the Amiga with a 68060 accelerator and a MAC emulator was the
fastest 68K-Mac you could buy, but today, it's an x86 computer with the
just-in-time-compiler. Sad but true...
ciao,
--
Jens Schönfeld
--
Author: Jens Schoenfeld
INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com
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