[fdutils] Need help with weird floppy issue

Donnie Barnes djbarnes at gmail.com
Mon Mar 6 21:09:01 CET 2006


On 3/6/06, Simon Owen <snowen at gmail.com> wrote:
>
> On 3/6/06, David C Niemi <niemi at tuxers.net> wrote:
> > Chances are, the 1.92 MB standard format and the one actually used on
> this
> > floppy are not at all the same.  How was the floppy formatted?
>
> Looking at the MAME source, src/drivers/system24.c, shows two track
> formats used:
>
> 2048+2048+2048+2048+2048+1024+256 = 11520 bytes
>   and
> 8192+1024+1024+1024+512+256 = 12032 bytes
>
> The first one is relatively easy to format as there's plenty of space
> for gaps.  The second one (which includes the 8K sector Donny
> mentioned) is very tight, with only 468 bytes (max) left for gaps.  I
> can't find any way it'll fit on a normal track, even using larger gaps
> and overlapping sectors.


Dammit, I looked all over that file (and others) in the MAME source and
didn't see that.  It probably wouldn't have helped me anyway, since I know
next to nothing about this low level floppy stuff.

The only way I've managed to format tracks like these on the PC is
> with a modified drive that spins slightly slower, increasing track
> capacity.  Or perhaps the original disk can be repaired by writing
> data into the existing sector format, assuming the headers are intact?


It's been reported that the floppy drive on the Sega machine *is* a standard
PC drive, but I can't confirm that personally.  It is well known that using
an actual Sega machine is the only way to copy a disk, too.  So in theory it
is possible for a standard drive to do it, assuming that the reports of a
normal PC drive working are correct.  That said, it could be that a normal
PC drive dropped in a machine will read it, but won't work for copying or
something.  I don't know.

Simon, I got your other mail, too, and can provide the image that MAME uses
if you need it.

David, yes, I am "the" Donnie Barnes.  Red Hat ran me off at the "right"
time, so I've just been raising a couple kids and tinkering with car racing
and pinball machines since then.  Still run FC on my personal laptop and my
servers and do tinker with Linux stuff from time to time.  I'll never not
use Linux, that much I know.  I do have a Mac and a Windows box on my desk
for some random stuff you can't really do with Linux (annoying desktop
crap), but one day...


--Donnie
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