🚀 go-pugleaf

In article <1991Jun18.050747.26870@bronze.ucs.indiana.edu> rschmidt@copper.ucs.indiana.edu (roy schmidt) writes:
>Chris Genly writes:
>>    1) Why can't I format a DS HD diskette as a DS DD disk?
>>    
>  The DS HD diskette uses a different type of medium for recording.  It
>is designed to hold a weaker magnetic "charge" for each bit written so

Actually it's the reverse of that.  HD disks of both sizes have a
higher coercivity magnetic medium.  This means the write current has to
be higher, not lower.  Trying to format a HD disk to DD may fail as the
write current may not be high enough to write data reliably.
Coercivity for 5.25" HD is about double that for DD.  Try to format a
DD disk as HD may fail as bit density is too high, and it lacks the
coercivity to retain the magnetic field.  In practice either can be
swapped for the other, results will vary based on the drive and
floppies used.  In general, it's a good idea to not cross format
HD and DD disks.  I've only done it under duress.

>>    2) Is there a slot or hole somewhere in the floppy jacket that tells
>>       the drive what capacity disk is inserted?
>
>  Not on the 5-1/4" disks.  The difference in medium is only important

In recent years HD floppies almost never have a hub ring, will DD
always do.  In the past this was not true, so it's certainly possible
to find a DD disk without a hub ring.  As far as a I know, no drive
can detect a hub ring.
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