A high speed, small size magnetic drum memory unit for subminiature digital computers

Abstract

A Memory with dimensions compatible with microminiature assemblies is required for future computers to be used in missiles and aircraft. A drum memory is described which can fulfill this need. The bit rate of 546 kc makes possible a 20-bit serial word time of the order of 40 microseconds. For a computer with add and multiply times of 40 microseconds, the drum memory described is adequate. Moreover, the technique described can be extended to provide a 20-microsecond word time by doubling the rotational speed of the drum, and to 10 microseconds or less by reading out two or more bits in parallel. A memory capacity of 15,000 twenty-bit words is available in the 7.4 X 3.7 X 3.7 inch total unit size, which is adequate for the type of computations usually made in an aircraft or missile. The advantage of such a drum memory as compared with a ferrite core memory, for example, is in cost, size, and ability to perform over wide temperature ranges. The disadvantage of the lack of immediate access to any address can for the most part be overcome by suitable programming precautions.