5 1/4 diskettes available

[Fred Cisin]

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