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List:       classiccmp
Subject:    Re: Up for Auction: Memory from the First Computer in Space
From:       Brent Hilpert <hilpert () cs ! ubc ! ca>
Date:       2015-10-31 6:36:57
Message-ID: F4150749-AEA1-4743-8301-2B86240767A0 () cs ! ubc ! ca
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On 2015-Oct-29, at 10:22 AM, Jon Elson wrote:
> On 10/28/2015 11:48 PM, Brent Hilpert wrote:
> > Very interesting to hear of another scheme, but it's not clear whether it applies \
> > to the Gemini auction memory. The BiAX scheme shows cores with the holes \
> > (apertures as they're called in the business) perpendicular to each other. In \
> > contrast, the Gemini auction cores have two apertures with the same orientation \
> > (a figure 8). 

> Yes, but I'm pretty sure the concepts are related.  The remanent flux in the \
> non-volatile side of the core affects the flux hysteresis in the volatile side, so \
> when you flip the flux polarity on the volatile side, you can see some effect \
> caused by the non-volatile side.

At  a general level, as you suggest, they could be said to be related, however what \
description is out there does seem to indicate them being distinct in the detail.

Refs on this page:
	http://www.ibiblio.org/apollo/Gemini.html
refers to the Gemini memory as being of the MARS type  "Multi-Aperture Readout \
Sensing".

MARS is described here if one wishes to delve into the magnetics:
	http://www.computer.org/csdl/proceedings/afips/1961/5058/00/50580443.pdf

A cursory description of BiAX
	http://encyclopedia2.thefreedictionary.com/Biax
does describe different functional principles as suggested in one sentence here:
	http://adsabs.harvard.edu/abs/1961P%26SS....7..184W

Photos of the Gemini auction memory:
	http://historical.ha.com/itm/explorers/gemini-3-flown-random-access-non-destructive-readout-4096-bit-memory-plane-from-the-gemini-spacecraft-computer/a/6146-52008.s
 See the third photo for detail.

. . and a photo of BiAX cores:
	http://www.computerhistory.org/revolution/memory-storage/8/253/984

While researching this I ran across a couple of other patents for multi-aperture \
techniques. A fair effort seems to have been put into developing a non-desctructive \
readout for core memory, to little effect in the marketplace. Looking at the photos \
one can see why, it looks like the methods doubled or better the complexity of \
construction, so the 'standard' core memory techniques remained the most \
cost-effective.

Amusingly, there was also a magnetic core device called a "transfluxor". Take that, \
flux capacitor.

I like this one however, another technique for NDRO, using standard core \
construction, from the 50s:   \
http://www-isl.stanford.edu/~widrow/papers/j1954aradio.pdf The magnetised core acts \
as a non-linear mixing element for two RF signals sent down the matrix wires. The \
magnetic polarisation of the selected core affects the mixing in such a manner that \
the phase of the difference/beat frequency can be observed to determine the \
polarisation and hence the stored-bit contents.


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