> When a drive seek fails, the drive first tries to read the halftrack (recall
> that Commodore disks are 48 tpi, not 96), then BUMPs out and back, tries to
> read the sector, tries to read the half-track again, BUMPs out and back, and
> so on, until it reaches a flag value stored in drive RAM, at which point it
> declares the error. Very noisy, and the drive light flashes randomly during
> this process.
Basicly the same on the Apple - just with a bigger problem: The
Disk ][ did 4 steps for every track, so quater tracks, and wrong
positioning by a quater of a track was possible. With some drives
the read signal was still readable a quater track aside, so you
could end up with a somewhat working disk where some tracks where
maladjusted - a horror when exchanging. Later on this was also used
as copy protection, to shift tracks - And there was also a programm
that modified DOS to write tracks closer (only 3 steps). Of course
completely incompatible, and _very_ drive and disk quality dependant.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
Received on Fri Jan 15 1999 - 14:24:23 GMT