On Mon, Mar 24, 2025, 2:59 PM Gregory Beat via cctalk <cctalk(a)classiccmp.org>
wrote:
TEAC FD-55F floppy drives
https://retrocmp.de/fdd/teac/fd55f.htm
The TEAC FD-55F never appeared in the world of IBM compatible computers.
Why is that? Because it was simply superfluous in the DOS world.
The TEAC FD-55F is a double-sided 5.25 inch drive that can write 96 tracks
per inch (TPI) with 9 sectors per track. In other words, the capacity of a
floppy disk is 720 KByte.
There were Radio Shack and other computers (NCR, etc.) that used this
format (DSQD).
Thr DEC Rainbow too. I upgraded by RX50s to a pair of these. There are
patches to 2.11 and 3.10b for 800k floppies. But it wasn't long after that
that I got a 38MB hard disks and i went back to 400k floppies.
The RX50s just had different padding between sectors so 10 would fit per
track. All the other parameters were the same.
If you didn't want to boot off the floppies, my IMPDRIVE package could
read, write or format them.
I pulled them out of storage during covid, but couldn't make them work
reliably again. :(.
Warner
This corresponds to the capacity of the standard 3.5-inch double-density
(DD) drive.
The 3.5-inch floppy disk format was supported since DOS version 3.2.
Introduction of 3.5” drives and disks by IBM (mid-1980s) was one reason
why the 5.25 inch drives with 720 KByte storage did not find their way into
the IBM world.
==
Further in the above web link:
Changing a Teac FD-55GFR drive to a FD-55F drive ... or,
How do I get my drive to spin at 300 RPM instead of 360 RPM ?
gb