Re: Did Commodore cheat with the quad density floppies?

Den Wed, 02 Jan 2019 15:34:24 +0100 skrev André Fachat <afachat@gmx.de>:
> Hi there,
> 
> I was looking at floppy disk recording schemes and I am wondering if
> the 8050/8250/1001 floppy disk format with over 500kB per side was
> actually out of spec of even the Quad Density disks?
> 
> The recording frequency was increased from 250kHz to 375kHz (× 1.5,
> for the innermost i.e. most critical track/speed zone). That resulted
> in a much increased number of bits per inch. See here:
> https://extrapages.de/archives/20190102-Floppy-notes.html
> 
> What do you think?

Afaik the 8050/8250/1001 drives are supposed to use "QD" disks, which
seems to be a format that's supposed to handle a higher density than DD.

It seems common for people to think that QD was a marketing thing used
for 96TPI DD disks, but I've seen so many 96TPI disks marked DD and
only a few (like one or two, and it was last summer that I first saw
them) disks actually labeled QD. (They contain a book keeping software
package, in Swedish, from the Swedish Commodore importer Datatronic.
Will be preserved as soon as I get my 8050 up and running, which has
been waiting a while for me to find my stash of IEEE cables :) )).

It would be really strange if floppy media didn't evolve the same way
as magnetic tapes did. With media good enough for 250kHz at track 35
when the 5.25" floppys were new, and soon good enough for 250kHz at
track 40, it seems reasonable that some years later the media used for
those drives were actually good enough for 375kHz at the 48TPI
equalient of track 35, which almost is where the highest track number
on a 77 track 100 TPI drive will end up.

(At some point in time a market for cheap rather crappy disks seems to
have evolved though, but those were probably anyway nothing people used
in their 8050/8250/1001 drives).

(Everyone who's been around long enough to remember cassette tapes from
the 70's and the 80's remember that before tapes like Maxell UD and
similar the standard / ferro / type I tapes did really sound crap with
a high noise level and muffled treble. Then something happened in the
late 70's and early 80's, resulting in more and more kinds of tapes
getting a lot better, and at the start of the 90's basically almost all
tapes had a decent sound even though there were of course still
differences between them).

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