> 3. The third realistic possibility is a marginal floppy drive, one that
> can't quite manage to read the additional tracks that the 1680 format
uses.
> If the target hardware uses a standard floppy drive, you might see if
> swapping in a newer one improves the device's performance.

For the record, the 1680K format does not use extra tracks on the floppy, it
simply reduces the "inter-sector-gap", or the blank space between data
sectors on the floppy.  Conventional 1.44 Meg floppies have so much blank
space between the sectors, you can squeeze another 3 sectors of data per
track onto the disk.

IIRC, the reason the inter-sector-gap for "standard" 1.44 Meg disks is so
big has something to do with limitations of some really early floppy
controllers (maybe for the XT platform?), and the requirement to do some
floppy I/O tasks in software (with what would today be considered REALLY
SLOW processors).  Mac's have used exactly the same linear bit density as
PC's for ages, and gotten nearly 2 Meg on a disk, rather than the typical
1.44 Meg for PC's, due partly to a more reasonable inter-sector-gap, and
partly to a "zoning" scheme similar to that used on Hard Drives, putting
more sectors/track on the outer tracks.

Anyway, there could still be hardware problems at fault.  Typically,
problems like this can be caused by alignment errors (ie the read/write head
is not over the center of the track on the drive used to read the floppy,
write the floppy, or both), or (much less common), a problem with the write
or erase head gap width on the floppy drive used to write the disk image.

Charles Steinkuehler
http://lrp.steinkuehler.net
http://c0wz.steinkuehler.net (lrp.c0wz.com mirror)


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