1.2/1.44Mb floppies

[John B. Milton]

In article <4194 at applga.aa.cad.slb.com> barber at applga.UUCP () writes:
>
>Has anyone found a clean way to use a 1.2 Mb 5.25" floppy drive or a
>1.44 Mb 3.5" drive with the 3B1?  I know people were working on it
>but I don't remember hearing any results.

This was going to go onto my HD expansion board, but I backed off on it. There
is no really clean way to do it, and no way to have BOTH high and low density
without a kernel change. The problem is part hardware and part software. There
is an 8"/5.25" pin on the WD2797 floppy controller chip, but because CT chose
to use the 2797 instead of the 2793, there has to be some off chip work with
the clock. The chip needs a 1MHz clock for 250kb/sec (normal density), and a
2MHz clock for 500kb (high) density. This is the easy part. The tough part is
retuning the external analog portion of the PLL tuning circuit, and this is
more than twice as tough if one attempts to be able to switch back and forth
from 250kb and 500kb under software. Tough, but not impossible. I have an S-100
board that does it just fine.

The biggest problem is time. I have far too many irons in the fire at the
moment. I am not going to start on any other harware projects until the hard
disk expansion board has settled down.

John
-- 
John Bly Milton IV, jbm at uncle.UUCP, n8emr!uncle!jbm at osu-cis.cis.ohio-state.edu
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