On Wed, 13 Apr 2022, Paul Koning wrote:
Indeed. Though even that is hard for the more exotic formats, if
original controllers are unavailable. How would you read, for example,
an IBM 1620 or CDC 6600 disk pack, given that the machine is hard to
find and those that exists may not have the right controllers? But both
are certainly doable with a "generic" track extractor engine. Turning
track waveforms into data then becomes a matter of reverse engineering
the encoding and constructing the software to do that. This may be
hard, or not so hard. For example, if you wanted to do this for a CDC
844 disk pack (RP04/06 lookalike but with 322 12-bit word sectors) you'd
get a lot of help from the fact that the source code of the disk
controller firmware, and the manual describing it, have been preserved.
Then as you said the real goal is to recover files, which means also
having to reverse engineer the file system. That too may be documented
adequately (it is in the 6600 case, for example) or not so much (does
such documentation, or the OS source code, exists for the 1620 disk
operating system?).
Some projects are well beyond the reach of even the most insane of us.
I don't think that any of us here today have the ability to build a
replacement drive from scratch. Even with full access to the original
construction documents.
Now, if we had NSA level of facilities, . . .
It certainly seems that it would be THEORETICALLY POSSIBLE, with an
extreme budget, to build a high resolution device similar to the 3M
Magnetic Tape viewer, . . .
https://blog.adafruit.com/2020/03/01/the-magnetic-tape-viewer-see-the-sound-on-a-tape/
. . . and use it to make optical imaging of the magnetic recording,
followed by non-trivial analysis to decode that into track images, and
then ultimately deciphering the encoding, track structure, and then
directory structure, . . .
It is certainly not feasible now, but someday, . . .
I have a RAMAC platter!
It is seriously FAR too damaged to consider restoring it to usable form.
I was also told that it was extensively "degaussed" when it was
discarded (possibly by Zellerbach Paper).
100 cylinders (with 100 heads in assembled structure), holding 5 million 6
bit characters, or a bit less than 100K per platter.
So, I am making a 24" patio table out of it (under 3/8" tempered glass).
http://www.ed-thelen.org/RAMAC/RAMAC_Plaque_v40.pdf
When Khrshchev was denied access to go to Disneyland, they took him on a
tour of the RAMAC factory, "to make up for it". _I_ would rather be at
the RAMAC factory in 1959 than at Disneyland, but the Khrushchevs were
disappointed.
--
Grumpy Ol' Fred ci...@xenosoft.com
