The NORAD SAGE Air Defense system I worked on for several years had 2 computers (one active and one standby). Each computer had 12 "magnetic Drums" which were essentially the predecessor to the later flat hard drives. Each drum had six sets of read-write heads that were staggered and mounted around the outside of the drum. Each set had 33 heads for the 32-bit word, plus a parity bit. The total capacity of 1 drum was, if memory serves, 150k words. Aligning these heads was such fun!
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