"hashi" wrote in message
news:Xns9623D2A674440776852d3f2@news.aioe.org...
> I have a floppy disk that I have discovered has unreadable sectors, some
> experimentations with this disk has shown some strange things I hope
> someone can explain.
>
> The drive doesn't seem to be able to tell that it is writing to the bad
> sectors so, when I copy a file to the disk, no errors result. I want to
> confirm that the data on the disk is good, so I try to compare the file on
> the disk with the original. When I try this, though, the compare succeeds,
> but, produces no floppy disk access. If I go do something else for a while
> and come back to it and compare again, now I get floppy disk access and
the
> compare fails with an os message "cannot read from the specified device".
> any subsequent compare I try fails, only a compare that occurs immediately
> after writing the file to the disk passes with no disk access.
>
> If I restart in msdos mode and try this, the first compare I try produces
> disk access and the compare fails.
>
> Why, in windows (win98), doesn't the first compare produce disk access?
and
> why do I get good data out of a file that is unreadable?

It's likely that win98 is retaining the data in a buffer in memory. When
doing the compare, the OS sees no reason to read the physical device since
the data it thinks it wrote to the disk is still in memory. It therefore
compares the buffer in memory to the data it was trying to write to the
device IMHO.