ferrite core memory
ferrite core memory
(storage)A single core could be selected and magnetised by passingsufficient current through its horizontal and vertical wires.A core would retain its magnetisation until it wasre-magnetised. The two possible polarities of magnetisationwere used to represent the binary values zero and one.
A third "sense" wire, passed through the core and, if themagnetisation of the core was changed, a small pulse would beinduced in the sense wire which could be detected and used todeduce the core's original state.
Some core memory was immersed in a bath of heated oil toimprove its performance.
Core memory was rendered obsolete by semiconductor memory.
For example, the 1970s-era NCR 499 had two boards, each with16 kilobytes of core memory.