idea for a universal disk interface

[Fred Cisin]

>> 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     		cisin at xenosoft.com