【NTT】 GEMMY High-Speed, High-Capacity Magnetic Disk Memory Unit

The Electrical Communication Laboratories (ECL) of Nippon Telegraph and Telephone Public Corporation (now NTT) aimed to improve the performance and economy of file memory, which accounted for a large share of system cost, and in 1984 started development to increase the capacity and speed of magnetic disk units while developing the DIPS-11/5E Series. In 1986, they achieved practical application of a high-capacity, high-speed magnetic disk unit (commonly referred to as GEMMY: Giga-byte capacity magnetic memory).

GEMMY had the features indicated below. It had a memory capacity 2.8 times that of PATTY, which had one of the highest capacities in the world, and achieved world-class performance in terms of surface recording density, data transfer speed, and other characteristics.

1) While improving the performance of the thin-film magnetic disk developed for PATTY, the research center developed a new thin-film magnetic head for high-speed operation and thereby achieved a surface recording density of 62 Kbit/mm2 and a data transfer speed of 4.4 MB/s.
2) The performance of the floating head in following the disk surface was greatly improved by shortening it to 3.2 mm and making it lighter (1/2 the weight of the head in PATTY).
3) High track density was achieved by controlling mechanical vibration. This was done using a HDA with a symmetrical shell structure, and a dual-support spindle configuration.
4) High-speed positioning with an average seek time of 12 ms was achieved by using a compact dual-actuator employing new materials, and feedforward positioning control.
5) High-speed access was achieved via high-speed data transfer at 4.4 MB/s, dual actuator control, and improved functionality of dynamic cross-calling to ensure effective use of access paths.

GEMMY high-speed, high-capacity magnetic disk memory unit with world-class memory capacity of 8.8GB.