RE: Reading 8x50-floppies with 1.2 MB-drive?

From: Baltissen, R (Ruud) (
Date: 2001-11-26 15:24:24

Hallo Levente,

> 8x50 ---> 1571: 100tpi mech vs. 48 tpi mech,

I still must be tired because when I wrote that part about using the 1571: I
was convinced in some or another way that the 1571 could do more TPI as it
is the "double" of the 1541. Completely forgot the "double sided" feature :(

> 8x50 ---> IBM 1.2M: mechanically incompatible (100tpi vs. 96tpi)

It seems I'm awaking up. My initial reponse was "That's only 4% !!!". Then I
realised how stupid this answer was. 

OK, forget about reading 8x50-floppies. But there is still the fact that the
drives have no eternal life.

Experiments with a MicroPower 2000 drive learned that it is possible to
read/write 1541-floppies with a normal 360 KB drives. AFAIK a drive does
nothing special with the bitstream fed to the drive except manipulating it
so it can be fed to the head. Somewhere on the board of every (older) C=
drive this bitstream is generated as well. One could tap it and feed it to
the appropiate pin of the Shugart-bus of the drive. Same for reading data.

Another matter is stepping the head. An idea could be cutting some wires and
connecting the steppingmotor directly to the original C= circuit. Another
idea is creating a circuit that translates the two steppingbits into a
direction and a steppulse for the Shugart-bus. Big advantage: now you can
use any type of drive.  Why this idea? Now I can replace the original 1.0 MB
drive with an 1.44 MB drive. This means on its turn we still can keep using
programs expecting to find big 1.0 MB drives.

I'm not sure but I vaguely remember someone expressing the idea about this
circuit before. If so, anyone knows if it ever has been developed?

   / __|__
  / /  |_/     Groetjes, Ruud
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