A high-speed read only store using thick magnetic films

This paper describes a high-speed, magnetic film, read only store of about 300K bits. The device and its implementation into a system have many unique advantages, including loose magnetic tolerances, minimal delay in the cell, linear drivesense coupling, and ease of information change. The basic device consists of a thick, anisotropic magnetic film sandwiched between the conductors of a strip transmission line. The cell utilizes the coupling between parallel word and sense line sections obtainable through the hard axis characteristics of an anisotropic permalloy film to store a binary ONE state. For a ZERO the coupling is inhibited by saturating the film with a small permanent magnet. Switching of the film can be described qualitatively, and to a large extent quantitatively, by a quasistatic analysis. A dynamic analysis describes the behavior of the film more completely and aids in optimization of some film parameters. The ROS system is designed in four planes of 256 words by 288 bits each. A single array plane was built and tested with a cross-section of drive and sense circuits. Because of the linear drive-sense relationship, the array can preferably be driven with a low current directly from a logic stage. The worst-case access time, including one level of decode, was measured to be 19 ns; the corresponding cycle time was 45 ns.