Rotating memory data recovery

From: Tom Jennings <>
Date: Sat Sep 11 16:20:17 2004

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

Practical suggestions appreciated...
Received on Sat Sep 11 2004 - 16:20:17 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:37:28 BST