1 Oct
1998
1 Oct
'98
10:04 p.m.
On 2 Oct 1998, Eric Smith wrote:
I'm not sure that would work for the protection
schemes that actually
wrote the sectors while the stepper was in motion. However, fortunately
that technique wasn't very common since the mechanical characteristics
of the stepper et al tended to vary somewhat from drive to drive.
Ah! I always assumed "spiral tracks" were simply quarter tracks written
every step of the stepper arm, and not while the stepper arm was moving.
In fact, I don't know how you could write bytes to the disk while the arm
was moving since the step had to be controlled by the program. Its been a
while since I messed with that level of detail on the disk drive but was
there any time to actually write bytes while the arm was being stepped? I
thought you simply poked the right locations and the head moved instantly
to the next step, no waiting required? Come to think of it, I believe
there was some pausing involved.
The other copy protection problem that simple attempts
at raw copying won't
solve is where the software expects arbitrary features of arbitrary tracks
to be time-synchronized. It's easy to build hardware that synchronizes
the index pulse (which the Apple doesn't even use), but that's not actually
sufficient.
Yep, synchronized tracks. Wizardry used this technique and it was one of
the most impossible disks to copy. I remember only ever being able to
make one bit-copy of it that worked.
Sam Alternate e-mail: dastar(a)siconic.com
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