[rescue] 3.5" floppy drive question(s)

[Curious George]

--- On Sat, 10/11/08, James Birdsall <jwb-tech at picarefy.com> wrote:

> Curious George wrote:
> > --- On Sat, 10/11/08, Curtis H. Wilbar Jr.
> <rescue at hawkmountain.net>
> >   
> >> Was wondering if 3.5" HD floppy drives can be jumpered/used in
> >> a system that only supports 720K, using them as 720K only
> >> drives ?
> >
> > AFAIK, if you cover up the hole in the medium that indicates
> > the medium to be "HD", the drive will sense it as a 720K
> > floppy and act accordingly.
> >
> > *However*, you will probably get less than ideal results this way.
> > IIRC, the data track on a 720K drive is wider than the *head* on
> > a HD drive.
>
> That was true for 5.25" drives, where they added more tracks
> (from 40 to 80) as well as more sectors (9 to 15). For 3.5"
> drives, the number of tracks is constant (80) but they doubled
> the number of sectors instead (9 to 18). The width of the head
> could be different too, but there's no 
> obvious reason why it should be. Everybody knew about the
> problems using a 1.2M drive to make 360K disks, but I don't recall
> hearing anything about similar problems with 1.44 and 720.

Argh!  My bad  :<  I use DSHD media in my Unisite with the
above trick -- but, as a matter of habit, always bulk erase
*any* media before repurposing it.  (So, if there *are*
problems, I'm immune).