ferrite core memory

ferrite core memory

   <storage> (Or "core") An early form of {non-volatile storage}
   built (by hand) from tiny rings of magnetisable material
   threaded onto very fine wire to form large (e.g. 13"x13" or
   more) rectangluar arrays.  Each core stored one {bit} of data.
   These were sandwiched between {printed circuit boards}(?).
   Sets of wires ran horizontally and vertically and where a
   vertical and horizontal wire crossed, a core had both wires
   threaded through it.

   A single core could be selected and magnetised by passing
   sufficient current through its horizontal and vertical wires.
   A core would retain its magnetisation until it was
   re-magnetised.  The two possible polarities of magnetisation
   were used to represent the binary values zero and one.

   A third "sense" wire, passed through the core and, if the
   magnetisation of the core was changed, a small pulse would be
   induced in the sense wire which could be detected and used to
   deduce the core's original state.

   Some core memory was immersed in a bath of heated oil to
   improve its performance.

   Core memory was rendered obsolete by {semiconductor} memory.

   For example, the 1970s-era {NCR 499} had two boards, each with
   16 {kilobytes} of core memory.

   (1996-03-04)