Rotating memory data recovery

From: jim stephens <>
Date: Sun Sep 12 01:28:26 2004

John Bohner and I have two additional drums from LGP-30's that need
same treatment. Any ideas could be put to use on more than a single system
if feasible.

Any ideas of comparitive characteristics of these system's drums?

There is also an additional system in the San Diego Compute Museum


Tom Jennings wrote:

> OK, I'm very close to needing to suck the data off the main memory of
> this LGP-21 before I reform caps and all that electronicky stuff.
> It would be nice to have a 16-bit MHz A/D system, but I don't. Any
> *practical* suggestions for someone with an extremely limited budget? I
> also don't have time to build one, though it's within my skills.
> (The LGP-21 I have has a rotating magnetic main memory; bit-serial 80KHz
> clock, 64 physical tracks (128 logical), 4096 31 (32) bit words, NRZ or
> NRZI. I figure A/D sampling of the raw head signal at 8 to 10 times the
> original clock rate will allow offline data recovery, should I smash
> data on later CPU powerup.)
> The platter is driven by an AC motor. It powers up completely
> independently of the rest of the computer, so I can easily do all this
> before I begin the restoration. I planned on rigging up a fast opamp
> buffer/amp, clip-leading it onto each head in turn (the heads are low-Z;
> I do know about ground, common-mode, etc), and taking 2, 4 or a dozen
> snapshots of each track. I'll make the track snapshots available to
> anyone who wants them.
> If there's anything there, it would be really nice to see
> 41-year-old-data.
> Practical suggestions appreciated...
Received on Sun Sep 12 2004 - 01:28:26 BST

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