On Fri 06 Jan 2023 at 22:06:42 +0100, Francesco Messineo wrote: > Now, the really puzzling part is: why I can't read the disks formatted > on the other 8250? All I get is 20 READ ERROR 39 0 > Things that I've checked: > DS0/1 start at 1/1 then change at tracks 40, 54, 65 > The GCR rom has the correct dump. > I've written a program that leaves the motor on, and can step in or > out by pressing a key on the PET, it seems the disks formatted on the > other 8250 have lower signal (as if alignment isn't really spot-on) > but the analog signal isn't too bad to justify a read error anyway. > Sync is clearly recognized or I would get a 21 and not a 20. Just a silly idea. I think you can probably see this with your scope. Is the disk you're trying actually formatted in 8250 format and not 4040? The bit speeds would be different, but maybe (just maybe) an incorrect speed SYNC might just be recognized? -Olaf. -- ___ "Buying carbon credits is a bit like a serial killer paying someone else to \X/ have kids to make his activity cost neutral." -The BOFH falu.nl_at_rhialto
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