An evaluation of design and performance of the permanent magnet twistor memory

A PERMANENT MAGNET twistor memory^1,2 for use in program stores with capacity greater than a million bits was first described 3 years ago.³ Memories of this basic design are used in electronic central offices and electronic private branch exchanges in the Bell System. Since 1961, more than 300 memories of this basic design have been manufactured for experimental, prototype, and production systems. This paper presents a timely review of the electrical characteristics achieved with the permanent magnet twistor memory, and discusses some recent experiments to evaluate factors controlling memory performance.