The Titan II ICBM / IIIC rocket guidance computer used magnetic core memory. Each bit is a tiny ferrite ring threaded on wires. Unlike most core stacks, this one used a flexible circuit board, so it opened like a book for repair. Two stacks, each with 8K words of 24 bits + parity.
Although the planes are mounted on the flex PCB, most of the core plane wiring is individual loose wires that go from board to board. According to GM’s patent, it should be possible to unfold the whole core stack into a single long strip. Just above the core planes are sense amplifier chips to read a bit from the plane. To prevent noise, a twisted pair (red/green) goes from the core plane’s sense line to the amplifier. The white chip is a resistor network to bias and terminate the sense line, connected to the black chip which is the amplifier. One advantage of the flex PCB is that the amplifiers are very close to the cores (as opposed to other core stacks where the amplifiers are on separate boards outside the core stack) so it reduces noise pickup.
From Ken Shirriff’s post
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