Hello David!

22 Dec 03 18:34, you wrote to CHARLES ANGELICH:

 CA>> That may be a factor but I'm not saying a drive that won't do
 CA>> an extended format is 'bad' or 'broken', only that certain
 CA>> drives did not allow the head to travel beyond the accepted
 CA>> 'last track' position while other drives did. :-)

 DD> Ah - I had an idea that the number of tracks was the same, and they
 DD> crammed more sectors per track....

The basic formats for 3.5" floppies are: 360k (1 Side, 80 Tracks, 9
Sectors/Track), 720k (2s 80t 9s/t), 1.44m (2s 80t 18s/t) and 2.88 (2s 80t
36s/t) - all of the extended formats are based on those 4 (actually the
last 3 - 360k didn't have any extended formats).

Mostly it went by increasing sectors/track like this:
For 720k  - 10 (800k), 13 (1.04m) and 14 (1.12m).
For 1.44m - 20 (1.6m), 22 (1.76m), 23 (1.84m) and 24 (1.92m)
For 2.88m - 39 (3.12m), 40 (3.20m), 44 (3.52m) and 48 (3.84m)

There were also attempts to increase capacity by increasing the number of
tracks, but those never became too popular because of problems with
compatebility and reliability:
For  720k 10s/t - 82 (820k) and 83 (830k) tracks
For  1.44 21s/t - 82 (1.72) and 83 (1.74) tracks

AFAIK, there were no formats for 2.88 floppies which used more than 80 tracks.
Also note that those "extended" formats are not some kind of a
standart, it's just a list of the most popular combinations.

Best Regards, Viktor (aka BlackDew)
 - bdew{at}mail.ru - 2:400/567 - ICQ 15553279 -

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