System 7: Has Bad-Sector-Checking Mechanism for Floppy Disks



System software version 7.0 seems to have a floppy disk formatting feature
that I haven't seen before.

If I format a new disk -- or reformat a previously used disk -- with the
"Erase Disk" option and the formatting is successful, there is a "Verifying
Format" function before "Creating Directory" appears. The boot blocks and
data space are filled with the pattern F6F6.

If the formatting fails part way through the process, and I try to format
again and it's successful, there is a "Re-verifying Format" function and
the pattern is PKKT.

I also noticed on some floppy disks, which I've reformatted several times
with the "Erase Disk" option, that the amount of disk space available
decreases, even though there are no files on the disk except the Desktop
file. I checked and there was a problem with some of the sectors. These
bad sectors showed zeros, while the rest of the disk had the PKKT pattern.

There is a bad-sector-checking mechanism for floppy disks in version 7.0,
and it is that mechanism that is using up the disk space.

The "Re-verifying Format" message indicates that there was a problem during
the first format attempt (a media failure was found on the floppy disk).
Most floppy disks don't exhibit this behavior. Any that show the
"Re-verifying Format" message multiple times would be suspect. You would
most likely find more and more problem sectors with the zero pattern as the
system tries to keep the floppy disk usable.


Published Date: Feb 18, 2012