🚀 go-pugleaf

Don Locke wrote:

>It works by stepping through the floppy.  But how does CHKDSK A: work? 
>It doesn't appear to step through the floppy & is very fast.  It appears 
>to me that it is reading some structure to get the information.  Maybe 
>the FAT?

Yes, the FAT and the Directory structures.
It compares each Directory entry with the FAT, and also ensures that
Every FAT entry is either empty, or covered by one-and-only-one
directory entry.
(More than one is a cross-link, Zero is a dropped file)

What you are doing is more along the lines of ScanDisk's Surface Scan
than ChkDsk.

From your description, it sounds like your backup library is checking
the drive statistics (GetDiskFreeSpace, Free Clusters value), and
trying to match it to what a pristine floppy should be. Thus, if any
file is present (maybe a "lost" file), or there is a bad sector
(entire cluster is marked bad for a single bad sector), the values
won't match up.

If you really want to do a surface scan, you should be able to tweak
the performance. 25 years ago, I was able to read 9" floppy disks at a
rate of 3 tracks in 4 revolutions while the standard was 6 revolutions
Reason for poor performance was due to head movement.
When you finish reading last sector on a track, the head moves to the
next track, and if you try to read the first sector, well, it's
already gone by. so you have to wait for it to come around again.
In those days, I found that by trying to read 1/3 of the way into the
next rack, that the heads would be there in time. Thus I could read 3
tracks in 4 revolutions by reading 1-12 then 5-12-1-4 then 9-12-1-8

It would take some head scratching, but might be worth the bother if
you are going to use it much.