[Coco] Floppy Disks

[Alex Evans]

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 = ?