IBM 62GV / STC 8800 Super Disk

1975 IBM 62GV / STC 8800 Super Disk
1st HDD’s to use an electronic rotary actuator to position magnetic heads

Why it’s important
The rotary actuator’s improvements in cost and physical size are now utilized in all HDDs in current production. Both products had first production shipment in 1975 and at this point it is not possible to determine which one was first. It should be noted that the first usage of rotary actuators in disk storage occurred in the 1960s.

General discussion
The first known instance of the application of a rotary actuator to a disk drive was in US Patent 3,172,082 filed by Gerhard Dirks more or less simultaneous with the RAMAC invention, see Disk Drive Patent. The invention was not known to be a commercial product.

An hydraulic rotary actuator was first used in disk storage in the Bryant Computer, Inc. Model 320 Disc File first shipped in November 1960 [1964Disc] and then in the follow on Model 4000 (advertised in Datamation, October 1963). Linear actuators of several kinds dominated disk storage from the original RAMAC into the 1980s. During the the 1980s there was much debate in the industry over the relative merits of rotary (lower power, vibration and cost) versus linear actuators.(less head skew off of a track), but by the end of the 1990s there were no new linear actuator designs.

In spite of the early disclosure and usage rotary actuators did not start into use until the middle 1970s and became the dominant design by the middle 1990s.

IBM 62GV Discussion
Developed at IBM's Hursley UK laboratory under the code name Gulliver. The initial capacity of the Gulliver file was 5MB. There were two heads on the actuator on the top surface and 8? fixed heads on the inner half of the lower surface. The rotation speed was 2964 rpm using a standard ac motor connected to the disk spindle by a belt. Subsequent models had 10 and 14 MB capacities
First customer shipment: May 1974
Capacity 5 MB
Tracks per inch (TPI): 167
Bits per inch (BPI): 5650
Shipments thru February 1990: 177 000

Superdisk Discussion
Developed by Storage Disk Corporation; the company was acquired by Storage Technology Corp. and the product was announced, Oct 13, 1975 as the the '8000' series disc storage subsystem. First customer shipment occurred in 1975.

Additional information
CHM Oral History of Terry Johnson re: Superdisk
CHM Oral History of Roy Applequist re: Superdisk
US Patent 3,824,572 - filed, Oct 19, 1973, Jim Morehouse
US Patent 3,864,747 - filed, May 5, 1973, Ivan Pejcha
US Patent 3,864,750 - filed, Oct 19, 1973, Roy Applequist
US Patent 3,883,894 - filed Oct 19, 1973, Terry Johnson
US Patent 4,019,205 - filed Sep 16, 1974, Salmond et al, "DISC DRIVE WITH ROTARY ACCESS MECHANISM"
[1964Disc] "Characteristics of the Bryant 4000 Series Disc File" in Disc File Applications, American Data Processing Inc, (c)1964, p.29-51
Case, W J P,

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