Plated wire memory--Present and future

Magnetic film and ferrite core memories will profitably coexist for at least the next three to five years. Relative to other magnetic memory elements, plated wire advantages include higher speed, lower switching energy, lower cost, and NDRO (nondestructive read-out). Magnetic annealing in a 30-Oe easy axis field at a temperature above 300°C for times of approximately 1 minute has solved the aging problem. A practical range of allowable magnetostriction coefficient values is maintained by holding a ±0.25 percentage point variation in nickel content. Plating a ternary alloy reduces by 2 to 1 the sensitivity of the process to electrolyte temperature. Use of a two-step (phase-modulated) writing process raises the threshold to creep approximately 20 percent and nearly doubles the easy axis wall motion threshold. Future plated wire memory systems are expected to have the following characteristics : 80- to 150-ns cycle time for 1 to 3 × 10
⁵
bits; 250- to 500-ns cycle time for 0.4 to 2 × 10
⁶
bits, and 500- to 1000-ns cycle time for 0.5 to 1 × 10
⁷
bits. The drive circuits will all be integrated and required to deliver only 200 to 400 milliampere-turns (mAt) of hard axis drive. A limited survey indicates the possibility of 3 × 10
⁹
bits of plated wire memory being produced in the United States in 1972.