10 Jul
2019
10 Jul
'19
8:27 p.m.
On Wed, 10 Jul 2019, Chuck Guzis via cctalk wrote:
While the hub ring is *generally* a good indicator of
"2D" versus "HD"
disks, I've seen exceptions. Early 2D floppies did not use the hub ring
and I've got a few HD ones that do. The hub ring thing is a story in
itself, which I've gone into in the past.
Since you could put on hub rings yourself (there were simple jigs from
Inmac, or the deluxe version of the Berkeley Microcomputer Flip-Jig),
If there is not a hub-ring, then it is an early "360K", or it is a
"1.2M".
If there is a hub-ring, then it is a an early "360K" with DIY hub ring, or
a later "360K", or a "1.2M" with a DIY hub ring.
OR, it is one of the exceptions.
Nevertheless, going by the probabilities, if it has a hub ring, then it is
PROBABLY "360K", and if it does not have a hub ring, then it is PROBABLY
"1.2M".
So, basically, what matters is how the cookie is
punched and what the
characteristics of the brown schmoo that it's been coated with.
High-density diskettes use a coating that contains smaller particles, is
generally thinner and of higher magnetic coercivity ("stiffer") nature.
If you hold two side by side, you may see a color difference.
Beyond that, you can forget the "tracks".
The same floppy can be used
in 80 track (96 track per inch) as well as 77 track (100 tracks per
inch) as well as 40 track (48 tracks per inch) drives.
and in this example, as well as TRS80 and Apple][, the 40 track could be
35 tracks.
Having said that, there *are* oddball exceptions, but
you're unlikely to
run into them in real life.
Such as the "Twiggy" for the Apple Lisa. A high density disk with
symmetrical (extra) access slot, to help make sure that EVERY disk had
thumbprints on the cookie. If you feel a need to see one, check with Eric
Smith.
Chuck has seen a higher percentage of the oddball ones than anybody else.
The 5.25" diskette or "Mini-diskette" is bar napkin size, because Dr. Wang
said that 8" diskettes were too big. I have not been able to track down
WHICH bar.
--
Grumpy Ol' Fred cisin at xenosoft.com