[Coco] Floppy Disks
alxevans at concentric.net
Tue Feb 8 15:44:27 EST 2005
There is always a lot of talk on the list about floppy disks. There
are a few things that I have found over the years, some of which
conflict with what others have learned over the years.
5.25" high density disks appear nearly identical to 8" double density
disks. The data encoding is identical at an identical rate, the disks
both spin at 360 rpm. Of course 8" disks typically have 77 tracks
while high density 5.25" disks have 80 tracks. If a controller chip is
designed for DSDD 8" floppies, using it to drive 5.25" DSHD floppies is
not hacking it beyond its design parameters.
5.25" HD media will not work in DD drives. If you manage to format
them at all you will likely have a number of bad sectors, and even the
"good" sectors will go bad very quickly.
3.5" HD media will work in DD drives. In the last several years before
manufacturers quit selling DD 3.5" media, they had gone to using
identical films with identical coating for both kinds of disks. In the
past I sometimes used HD media in DD drives and never saw any
difference in dependability. I have even run into a couple cases where
commercial software was distributed on HD media which had been
formatted DD. That said, if you format HD media to DD then try to read
it with an HD drive you will have problems unless you fool the drive
into thinking it is DD media. As a result I generally do not use HD
media in DD drives.
Theodore (Alex) Evans | 2B v ~2B = ?
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