Memory Tech you don't see very often

Paul Koning paulkoning at
Thu Jan 6 09:14:36 CST 2022

> On Jan 6, 2022, at 4:06 AM, Brent Hilpert via cctalk <cctalk at> wrote:
> On 2022-Jan-06, at 12:19 AM, Joshua Rice via cctech wrote:
>> Not cost effective at nearly $10,000! I understand they're very rare, given they were only used for a few years in industry and they're clocking on 3/4 of a century old, but even then, that seems an order of magnitude or two off the real value.
>> Actually, looking them up, doesn't seem they were used in much at all. Seems to have been a bit of a technological dead-end since core memory quickly superseded it with it's (relatively) cheap costs and (relative) ease of manufacturing. I imagine the US gov. probably used them somewhere, since they were a sucker for cutting edge technology of the time.
>> Would be interesting to know how many hours it's got on it
> "Not cost effective" ?  What does that mean in the arena of valuation of historic artifacts?
> No, they didn't go anywhere as a product and apparently only saw use in one machine.
> However, the 'pro' side of such a debate is that they were a very early attempt to produce a fast digital RAM memory specifically for use in Stored-Program Machines, at a time when memory was at the top of the list of problems in development of the first SPMs, and actually before any SPMs had been produced, and weren't a serial technology like drums and delays lines tortured into applicability for the task.

Yes, for example in van Wijngaarden's 1948 course text "principles of electronic calculating machines", the Selectron is explained in detail (as a 4k bit device, which apparently was the original hope).  It also mentions something like a Williams tube (not by that name, so perhaps it's not exactly that).  The only other idea for a random-access RAM that it mentions is a rather vague notion that a crossbar of gas discharge elements could be used.  That was later (1960) used as a display device, the famous plasma panel display invented by Don Bitzer et al.; not clear if it was ever actually used as a memory device.  Core memory does not appear in that 1948 document, that's a later invention but indeed the one that ended up successful in practice.


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