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/
On Thu, 14 Apr 2022, John Foust via cctalk wrote:
And how often do those antique viewers come up on eBay and at what price?
Modern ones are for sale for about $120:
https://store.arnoldmagnetics.com/product/284/magnetic-viewer-b-1022
Alas, although still a lot of it around, magnetic recording is not as
common as it once was, and increasingly, new technology is solid state.
So, there isn't any where near as much incentive to build devices other
than as novelties.
But you can't really use an optical method, right? You need to scan
the field another way.
If the entire artifact were drenched with magnetic disclosing fluid, then
it could be a simple optical capture. But the 3M device is truly
non-destructive.
It is only a tiny window. I am not aware of any 8" diameter versions of
it.
And if you set a limit on disk platter tech to anything made before 1985,
what's the magnetic resolution you'd need and what would you need to detect?
1985 would include 96tpi "1.2M" "high density", 720K 3.5" (135tpi), and
hard disks with at least 600 cylinders.
Could the reconstruction be software-based, reconstructing from data
gathered while scanning X-Y across surfaces using a mechanism not
unlike a scanner or 3D printer? Or would you need to scan like
the flying head that wrote the data back then?
Yes, if there is a good clean opticl image, then the software would have
to clean it up, including filling in by context for any uncertain spots,
and convert the concentric circles in the image into an array of lines
(tracks), decode the flux transition data into bit patterns (with a basic
understanding of FM, MFM, GCR, and a few flavors of RLL). At that point,
you would have a disk image comparable to what could be obtained by
examining the disk in a drive.
RAMAC 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
A rare item. How many others have you seen in the wild?
This is the only one that I have seen. I'm sure most decent sized museums
have one, or even an assembled multi-platter (FIFTY-TWO!) system.
I didn't even know that it was RAMAC until Mike Albaugh told me.
Wil Price had it at Merritt College in the late 1960s, in the
1401 room, and brought it along when the college moved up onto the hill.
I used it, core planes, cards, etc. in small history component of some of
the classes that I taught.
By the time that I was ready to retire (constructive discharge), the
college shifted its focus from programming to "Remedial Computer Literacy
For The Digital SweatShop", so I was the only one who could appreciate it.
--
Grumpy Ol' Fred ci...@xenosoft.com
