40k Ferrite Memory Core

Brent wrote: pins on each plane would be 2 and been wires making are also I agree with Brent's analysis. I too counted 21 planes, which seems a bit odd, as typically each plane represented one bit in a word structure, which would indicate a 21-bit word...not something that matches up with commonly-used word sizes in 50's/60's era computers (12, 16, 18, 20, 24, 32, 36, 48, 60 or 64 bits). Perhaps some of the planes have already been removed? It is possible that whatever machine used this stack didn't use the "bit per plane" methodology, and instead used a 48-bit word (Y aspect of matrix), which would mean that each plane held 40 words, for a total of 40*21 (840) words of 48-bits each. This stack would likely be just one of many used in whatever computer it was part of, in order to have sufficient memory to be useful. It is also possible that this stack was used alone in some type of peripheral device. Frequently devices like line printers, rotating memory controllers, and other peripherals of the '50's and early '60's used smaller arrays of core for buffering purposes, which may account for its rather unusual arrangement. from a I figure late '50's/early '60's. By the mid-60's, the size of the ferrite cores had been dramatically reduced. While the general construction was similar (in terms of 3D core stacks like this one), their physical size was significantly smaller by the mid-'60's. The reduction in the physical size of the ferrite cores was somewhat mandated by the use of transistorized driver circuitry. The amount of current required to "flip" a larger diameter core was sufficiently high that tube-type driver circuit was required in the early days of transistors. As the cores got smaller, so did the current requirements, which led to the practicality of transistorized X/Y/Inhibit drive circuits. The cores in this stack are large enough that as Brent suggests, the machine may have (at least) had tube-based drive circuitry, if not being a completely tube-based machine. Later, the three-dimensional aspect of core memory was changed, such that multiple arrays were woven into the same plane of core, making the core array fit on a single circuit board (typically with additional board(s) that provided the address decoding, constant current source, X&Y drive, sense, and inhibit functionality) in a 2-dimensional arrangement. Whatever this stack is from, it is definitely a work of art that should be preserved intact. Like Brent, I sincerely hope that it doesn't end up being reduced to 21 individual planes to "optimize" its sales value on whatever venue it is marketed under. Rick Bensene http://oldcalculatormuseum.com (where some of the old calculators have core memory, some 3D, and some 2D)