Magnetic Core Memory

Magnetic Core Memory [1] predominated as Random Access Memory (RAM) for computers for storing data and programs from the mid 1950s until around 1980. Toroids of a compressed ferrite material exhibited magnetic properties which conveniently permitted magnetisation in either a clockwise or anticlockwise direction to store a 1 or a 0 bit.

The source and date of the memory shown here is unknown. Judging by the transistors and core size (1.8mm dia), it was probably manufactured in the late 1950s. The transistor case was popularised by Mullard (UK) in the 1950s but their 1960 Transistor Reference Manual does not list a type "92PC".

The green wire threaded diagonally through all cores in the sense wire for reading. The red select wires are duplicated on the Y axis, perhaps to simplify the circuitry for writing and reading. The green wire in the X axis is the inhibit wire for writing a zero to a core.

In the top left of each core plane is a separate isolated core. I suspect this core acts as a filter on the sense wire and is held in place by a loop on an unused red wire.

Please let me know if you have knowledge of the source of this memory.