Generic 1.44Mb on PS/2 systems (was "Auction: Nice Model 77 on the bay")
- From: "David L. Beem" <David@xxxxxxxxxxx>
- Date: Mon, 11 Sep 2006 01:55:21 -0600
Hi Peter,
...I am going to work out a simple scheme to use a "generic 1.44MB FDD"We should talk. I've got an external generic 1.44Mb drive as A: on a
with the old machines. (With the emphasis on "Simple" !) It is not as
trivial as one might think. It is not only a matter of different
connection scheme (card-edge vs. pinrows) and drive power supply but also
a different approach in the media detection as well. Using a 1:1 cable
with only the power wires taken off will end up in a FDD that fails to
properly detect 720K diskettes. The turning point is Pin 2: -High Density
Select, which is an input on old PS/2 FDDs, but an output (from the FDD)
on genericas. Maybe I should use a Mod. 77 2.88MB instead ... ? There are
many of them around. Normally not much of a problem - but many option
disks are DD only and that makes updating of a reference diskette pretty
complicated. But what. I'm going to think about that for a while and play
around with my own 70-A21 again.
Model 50Z (well, the Industrial built around the 50Z planar. It was a
commercial drive package, with manual, to put a 5-1/4" on either the "Model
25, 30, 50, 60, [or] 80".
The circuit has two internal cables based on the model, actually being
confusing in the manual (they talk about putting the connection directly to
planar, supplanting the internal drive). Then from a DB-37 breakout (also
carrying drive power) it goes to the external case, with a handful of TTL
chips (there is also a switch that is set to one position for the Model 25 &
30, another for the 50, 60, & 80). "PROCOM" on the two circuitboards is
whited-out, with "copyright 1987" allowed to stay.
Currently I have a Panasonic double-drive in the external case. It has
both the 1.44Mb & 1.2Mb together in the same assembly. But I have to do a
few patchwires on the Model 50 riser to get around the built-in cable twist
for both drives to work.
I'll go through & test all the media in each drive once that is done.
The Model 50Z (as many of the other models I'm sure) doesn't have a setting
for the 1.2Mb & labels it as 1.44Mb. Otherwise there is a 360Kb external
selection too (to maybe stop some of your head scratching, I have heard that
the 720Kb drives won't work in some of the models >= 50).
David
David@xxxxxxxxxxxxx
.
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