Even SC+ is not able to make an identical copy of a
certain disk. As Jim Drew explained somewhere, the true
halftrack protection from Bounty Bob Strikes Back!
cannot be reproduced with the native copier for the SC+.
Instead Jim wrote a custom copier after he analyzed the
protection.
By analyzing a protection and then creating a mastering
routine that will recreate that protection does mean
that this is not a _copy_, but a re-master.
That is not the case. The Bounty Bob Strikes Back! Copier is an actual copier.
It is just a custom copier that knows which tracks are 1/2 tracks and which are not. Since the main copiers for Supercard+ do not support 1/2 tracks, a custom copier was
needed. Copying Bounty Bob Strikes Back! is a two part process - first you copy the disk with the GCR Nibbler and then you copy it again using the custom copier.
And further true copier machines (Trace duplicator) are
able to create patterns that can be detected with a 1541
disk drive, but cannot be written with 'em, even if you
do adjust the motor speed. E.g. true Fat Tracks that are
recorded over two adjacent halftracks. If you try to
replicate that, then you would always overwrite one of
the both halftracks due to mechanical issues. The 1541's
R/W head is a so named tunnel erasing head. It write a
wider track and after that the left and right side of
that wide track are erased again after. This sharpens
the track and it can be better reread after. In fact I
never saw such a true Fat Track protection, mostly these
were only precisely aligned adjacent full-tracks.
If you disable the erase head you can write a 1/2 track. However, you need to first erase the disk with a magnet. EA used true 1/2 track protection, with tracks 34, 34.5, and 35 all containing valid sectors for the entire track.
Reframing btw. is no magic issue. And because Jim Drew
does not explicitly tell about all the nifty tricks that
he used to make the copiers work does not mean that he
did not use something similar to reframing for SC+.
Since no 1541 drive runs at the very same RPM as the
drive the original disk was recorded for, you always
have to do SYNC and GAP length reducing/increasing,
maybe RPM adjustments and some sort of reframing or
frame detection (perhaps tail GAP detection too) on
SYNC-less tracks.
I never changed gap lengths or anything else GCR related, and I didn't re-frame any data. The only real change was a reduction of the drive speed to 298.1 RPMs.
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