5.25 floppies that read but don't write

Eric Smith spacewar at gmail.com
Thu Aug 20 22:35:54 CDT 2015

On Thu, Aug 20, 2015 at 9:01 PM, dwight <dkelvey at hotmail.com> wrote:
> If you are really interested in creating 360K disk, you must have a 360Kdrive.

And beyond that, sometimes trying to format or write to a "360K" (48
TPI) disk in a "1.2M" (96 TPI) drive does appear to work, and may even
appear to read reliably on the same drive, but it's *NEVER* going to
be reliable to read it on an actual 48 TPI drive.

The best case result is if you use a 96 TPI drive with a floppy that
has NEVER been written (even at the factory), and format it and write
at 48 TPI, that actually may read reliably on 48 TPI drives, because
it doesn't have remnants of normal-width 48 TPI tracks.  However, it's
still not recommended for obvious reasons.

Some people have claimed that they've been able to achieve the same
effect by degaussing the floppy first, but when I experimented with
that I found that even a supposedly high-power degaussing coil was
pretty marginal for actually erasing floppy disks. It definitely would
corrupt the data and render it unreadable, but it did NOT yield a
truly erased disk.

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