13 Feb
2013
13 Feb
'13
7:13 p.m.
On 02/13/2013 05:57 PM, Fred Cisin wrote:
The reason why DD disks work is because it IS DD!
"quad" is exactly the same on each track as DD,
just putting another identical track in between
each of the existing tracks.
An inspection of a random bunch of old floppies shows that labeling
varied between manufacturers such as "35/40 track vs. 70/80 track", "48
tpi vs. 96 tpi", etc. Oddly, manufacturers seemed to be silent on the
subject of 100 tpi drives, but 3M went to silly lengths, even specifying
the recording mode. For example, a 3M 744-0 floppy is labeled "48 TPI,
Double-sided, Single-density". (that particular sample has 100 tpi GCR
data on 77 tracks).
Although some, such as NEC, did strange things!
They run their HD ("1.4M") 3.5" drives at 360RPM (instead of 300RPM),
so that they can get the same ~1.2M format structure on 8", 5.25",
and 3.5"!
That makes perfect sense--it's the rest of the world that's strange.
There are high-density 5.25" drives made by Matsushita and a few others
that do not offer a low-density (250K) mode for use on the PC98 platform.
Some PC98 drive interfaces require "disk-changed", "ready", and
"in-use"
signals as well as drive select 0-3. It makes sense--the "in use"
allows software to determine if a drive is present, regardless of
whether or not it has a diskette inserted. "Ready" likewise makes
sense. It can be challenging finding replacement drives.
Try reading a Victor 9000 (aka Sirius) with ANY other
machine!
I can do it with my Catweasel-equipped machine.,,
--Chuck