One of the core memory boards <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/edyson/1001261">hanging in our office</a> collection… the industry standard for computer memory in the 1960’s.  Here you see 18 bytes of memory in 2x3 inches, where each hand-woven ferrite ring can be individually magnetized or not, representing 1 or 0.
<p>Until I took this macro zoom shot, I had not noticed the unusual wiring for the cores on the left.   The wiring on the right is standard to core memory arrays (to read and write a magnetic bit to the iron core at the intersection of a particular row and address line).
</p><p>The core memory arrays would often have parity bits for each data row (for error detection).  Perhaps the wiring on the left implements a parity operation. It has repeating loops across pairs of rows.  Does this look familiar to anyone?
</p>
(The only marking on the 7x9” board is Xak 4292.  It has 300 bits in the memory array, with 15 pairs of rows with 10 ferrite cores in each row.)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/44124348109@N01">Steve Jurvetson</a> from Menlo Park, USA
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/44124348109@N01/4480203/">Primitive Memories</a>