A nondestructive readout film memory

Abstract

A film memory system, utilizing BICORE memory elements and capable of nondestructive readout operation, was designed and built. Two thin films are used for each memory element: one of high-coercivity cobalt-iron alloy, one of low-coercivity nickel-iron alloy. The former is used to store the bit while the latter senses it. These films were vacuum deposited in a multilayer fashion onto a single glass substrate. The film cores are circular discs with a diameter of 0.050 in. and placed on 0.100-in. centers and fabricated in 16 x 18 arrays. A model memory containing sixteen 18-bit words was designed and constructed to evaluate the performance of this type of memory and to provide a device which could be used to rapidly test film core arrays. The design and operating characteristics of the memory are reported. Read currents can vary over a 2:1 range without producing errors. Temperatures and other environmental factors did not appreciably affect memory performance. Later, a 1024-word 36-bit memory using the same principle of operation was constructed and operated. Some of the design details as well as the preliminary results of this larger memory are reported.