I just realized that the toggling of pin 14 is thanks to the feature
of the uPD765/8272 that automatically polls all four drives. I mostly
have worked with WD controllers which don't do that.
So I still don't know why the TWOSIDED/ signal isn't being reflected
in ST3. I'll have to trace out how it
My references to pin 14 should have been to pin 10 for the TWOSIDED/
signal. Pin 14 is the SIDESELECT/ signal which was working fine.
In July 2014 I mentioned that I did some reverse-engineering of a Quay
900 computer system, based on the Quay 90F/MPS single-board Z80
computer and two CDC/MPI 9406 double-sided 8-inch floppy drives. Back
then I wrote a simple monitor ROM and a floppy disk formatter program,
but at the time I didn
