On Fri, 20 Sep 2002, Joe wrote:
> I was scrounging around last week and found a pair of HH 5 1/4"
> floppy drives that are marked "2.4" next to a disk symbol on the
> front. Just out of curiousity I picked them up and checked
> <http://marina.mfarris.com/floppy/Hitachi.html> and sure enough
Interesting that those guys refer to them as "high density", but refer to
the 1.2M as "double density"
> they're 2.4Mb floppy drives! I've never heard of these before. Does
> anyone know what the disk format is or where these are used? The
> drives are Hitachi model FD532EIU. The label on them says that they're
> made for IBM. They're in some sort of a plastic sled.
I'm not familiar with them, at all. I don't think that IBM ever
released a machine with them, like their 3.9" drive. It does not appear
to be supported in any version of PC-DOS. But a simple block mode device
driver is all that would be needed.
There have been a few different higher density 5.25" systems, such as the
one that Kodak bought out. But I don't think that this is the same one.
There are two obvious ways to get that capacity. One would be to halve
the track spacing to 192 TPI. That would give you 160 tracks per side,
with 15 sectors per track with 512 bytes per sector, and would permit
using "regular" 600 Oerstedt ("1.2M") diskettes, but possibly with some
problems with diskettes that aren't quite up to it. (like the problems
that Tony has with using "360K" diskettes for 720K 5.25.) It would
require a smaller step track to track, and a narrower head (about 1/2 mm
wide track v the 1/6mm wide track of the 1.2M)
The other way to do it would be to use a barium ferrite diskette (5.25
version of the 2.8M 3.5"). That would require a special head for
"vertical recording", and would require a 1000K bits per second data
transfer rate (same as for the 2.8M 3.5"). Then it would still only be 80
tracks per side, but instead of 15 512 byte sectors, it would be able to
fit 30 (or maybe even 32) 512 byte sectors on each track.
--
Fred Cisin cisin_at_xenosoft.com
XenoSoft http://www.xenosoft.com
PO Box 1236 (510) 558-9366
Berkeley, CA 94701-1236
Received on Fri Sep 20 2002 - 12:45:00 BST