Plane of core memory

dwight dkelvey at
Thu Apr 18 12:33:54 CDT 2019

I don't believe there is a simple non-destructive way to read the state. If you could remove the cores, I believe you could put each core in a weak magnetic field. As the field passes from side to side, one should be able to determine the direction of the saturated cores because one side would allow more of the field to enter the core while the other side would act as non-magnetic.
As for reading the data, you'd need to experiment to determine the minimum current that particular core required to flip a bit. With careful adjusting, I suspect one could sample the first bit.
Once knowing the levels used, the entire array can be read.

From: cctalk <cctalk-bounces at> on behalf of Jim Brain via cctalk <cctalk at>
Sent: Thursday, April 18, 2019 10:19 AM
To: cctalk at
Subject: Re: Plane of core memory

I am the enviable owners of a plane of memory (procured a few years back
at VCF-East, when there were a bunch of 32K? boards int he consignment pile.

(Sorry, not currently interested in selling :-)

But, I am thankful for the links, as I have wanted to interface this
with a CPU or PC of some kind.

A few questions, though:

  * Is there a way to "read" the core non destructively using any kind
    of passive method (I know, it would be tedious, no doubt, but I just
    feel like I should "backup" the core before I go messing with it)?
  * Along with the above, might there be a way to extend the passive
    read to be a worthy "exhibit" I could take to shows? Core memory is
    impressive just to look at, but reading it out using the PC and
    displaying the contents is so easy to fake that I think people will
    assume the core memory is not really being used.  Some way of
    showing the actual magnetic changes in a small matrix (the large
    plane I have is probably not a good candidate unless there is a way
    to show such minute cores fields) would I think make the exhibit far
    more interesting, especially if I arranged the grid in a square and
    created a really slow version of something like "Tetris" on the plane.

Ideas appreciated.


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