A magnetic-core matrix store with direct selection using a magnetic-core switch matrix

The paper describes the magnetic-core matrix store developed for a large high-speed digital computer, Edsac II. The store has a direct selection system for reading, and the access switch using a matrix of switch cores is described. The results of measurements to find the optimum operating conditions for the storage cores used are given, and circuit details of the storage unit are included. Design criteria are established for the size and winding details of the switch cores. The proposed permanent store for frequently used subroutines and constants is also described.