[fdutils] Need help with weird floppy issue

Simon Owen snowen at gmail.com
Mon Mar 6 17:38:09 CET 2006


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.

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?

Best regards,

Si

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