Floppy formatting and using

[Wolf N. Paul]

In article <439 at zinn.MV.COM> mem at zinn.MV.COM (Mark E. Mallett) writes:
>Are you suggesting that the Microport floppy problem is with bad
>sectors?  Bad sectors on floppies are extremely rare.  I expect that
>when I find a floppy with a bad sector, I need to find another
>floppy.  Problems with floppies on my SYS V/AT system are extremely
>common.  Even so, I specifically stated in my original posting (the
>reference to which seems to have gotten lost here :-) ) that I could
>format and use the floppies under MSDOS.  So that's not it, I'm afraid.

That could still be it -- DOS will let you use floppies with bad sectors,
it simply marks them as unavailable in the FAT. If you get a floppy with
bad sectors, and format it under DOS, the format program will report,


	XXXXXXX bytes total
	   XXXX bytes in bad sectors
	XXXXXXX bytes available

whereas Uport's format program is a low-level formatting program, which neither
verifies the formatted floppy, nor records bad sector information (how should
it, since it doesn't know anything about a FAT, or a freelist.

Any bad sector handling would need to be built into MKFS, not format;
it may require changes to kernel file system code as well - don't know.
and floppies with bad sectors ARE unusable for things like tar or cpio
which look at the floppy as a stream of sectors -- can't have gaps in that.

The other alternative is to write a floppy archiver, which verifies each
floppy before writing to it, and keeps its own bad sector info somewhere
at the beginning of the floppy. It can then be made intelligent enough to
skip these bad sectors when reading or writing.
-- 
Wolf N. Paul * 3387 Sam Rayburn Run * Carrollton TX 75007 * (214) 306-9101
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