🚀 go-pugleaf

In article <chris.3717@genly.UUCP>, chris@genly.UUCP (Chris Hind Genly) writes:
>     1) Why can't I format a DS HD diskette as a DS DD disk?

The HD drive lays down two skinny tracks where the DD drive lays down
one fat one.  The DD drive isn't capable of erasing the two skinny HD
tracks, as it misses one.  This left over track does interfere with
the read operation, as it's close enough to the head for that.  You
can reformat HD floppies as DD if you bulk erase them first, to erase
all the skinny HD tracks.

For this same reason, a 360K floppy written with a 1.2M drive cannot
be reliably read on a 360K drive, as the track written is too skinny
for the fat DD head in the drive.  And a 360K floppy formatted with a
360K drive cannot be reliably written with a 1.2M drive, as the HD
head is too skinny to erase the fat DD track.

>     2) Is there a slot or hole somewhere in the floppy jacket that tells
>        the drive what capacity disk is inserted?

Only on 3.5" floppies.  The presence of the hole indicates a 1.44M
disk.

>     3) What are the various diskette formats available now, and what
>        are thier capacities?

8" :	Your guess is as good as mine, but I think some of the 5.25"
	formats are supported.

5.25" : 160 (SS/DD 8spt)
        180 (SS/DD 9spt)
	320 (DS/DD 8spt)
	360 (DS/DD 9spt)
	640 (DS/QD 8spt) *
	720 (DS/QD 9spt) *
	1.2 (DS/HD 15spt)

3.5" :	720 (DS/DD 9spt)
	1.4 (DS/HD 18spt)
	1.6 (Sun workstations)
	2.8 (?)

* Not IBM standard, but I can read them on my IBM clone, and some
  Z100's use this format.

DJ
dj@ctron.com