I assume it's not easy to copy alignment disks, but I guess I will
find out.
It's actually not possible to copy them. Not for any "copy protection"
reasons, but just the very nature of the analog signal laid down on the
disk. No "regular" disk drive can recreate the signal.
Chuck had actually talked about how to make one on a VCF post a while back:
https://forum.vcfed.org/index.php?threads/greaseweazle-v4-reading-m1-5-25-fl
oppies-on-a-sa400a-drive.1242918/post-1380519. Didn't sound like it was
going to be as easy as copying a disk... ;)
On Thu, 3 Oct 2024, Chuck Guzis via cctalk wrote:
No, not easy, but possible, given skill, equipment and patience.
An analog alignment disk would be an impressive task.
Something similar to the Dysan Digital Diagnostic Disk would be far more
straight forward, starting with modifying a drive to be able to do precise
(micrometer) postitioning of the head away from the normal position.
Although far less precise and accurate than the analog alignment disk, . .
radial alignment is done by seeing which off center tracks the drive can
read. and adjusting it until it can read the same amount off-center in
both directions. If it can read disks off-center in one direction better
than disks off-center in the other diraction, that tells you which
direction the head/positioner needs to be moved.
The REAL dysan Digital Diagnostic Disk puts sectors on one track
progressively further out of position in alternating sides; calling for
reading an equal number of even numbered and odd numbered sectors. THAT
would be difficult, but recording entire tracks off alignment by a known
amount isn't so hard.
Some of the old-timers might remember a guy who was on this list a long
time ago, who claimed that the "copy-protectin defeating" program that he
used could copy ANYTHING, even alignment disks!
'course, he was also the one who claimed that his 1990's "Sentry 7?)
machine was the one that email had been "invented" on, that Valtrep was
the predecessor to FORTRAN, and that he had a tape of OS/2 for the
PDP(labeled "PDP OS/2").
Some of us speculated that that MIGHT actually be a backup tape from
somebody having been using a PDP to develop some software to run under
OS/2
--
Grumpy Ol' Fred ci...@xenosoft.com
