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.
