1962	IBM 1301
	1st disk drive with flying magnetic heads and one head per disk surface,

2/14/09

Why It's Important

The 1301 disk drive was a next generation of disk drive that followed the RAMAC. This device totally changed the concept of the disk drive to one with a head per surface with spacing set by flying heads on the spinning disk surfaces which has endured ever since. This design offered greatly increased capacity and much faster access time than the RAMAC 350, allowing real time applications in addition to capabilities to provide more complex business data processing. The 1301 technical advances and performance capabilities opened up the computer industry to the real potential of magnetic disk storage.

Brief History

The American Airlines Sabre system, for on-line real time airline reservations in the United States was the driving applications opportunity at which the 1301 was targeted.

The 1301 Disk Storage Unit began as the ADF (Advanced Disk File) in 1955 based on a a flying head per surface with perpendiular magnetic ecording usung probe heads and oxidized steel disks. A January 1960 audit concluded that the three new technologies it incorporated
1. a flying heads
2. a high-speed high accuracy hydraulic acyuator
3. perpendicularl magnetic recording
had not been integrated and tested sufficiently under laboratory conditions. In order to speed progress perpendicular recording was dropped and a number of personnel changes were made including: Al Shugart as Engineering Manager, Jack Harker as Air Bearing Development Manager of head-disk flying heads and Al Hoagland as Magnetic Recording Technology Manager. A return to longitudinal recording was made, the universal method used for drums, disks and tape.

The basic concepts of this disk drive were proposed by Jake Hagopian who realized the RAMAC design was a one of a kind approach and much shorter access times and higher densities would be required. His notebook as early as September of 1954 shows a flying head as well as a head per surface comb access.The major technical innovation of the 1301 was the the flying head. Jake Hagopian first thought of this and demonstrated the principle to everyone in the laboratory. He also chose the original approach of using perpendicular recording which in essence made him the "inventor" of the first disk drive with a head per surface. It was Harker's team including Russ Brunner, Bill Gross, and Ken Haughton that did the fundamental research to define stable regimes for such air bearing flying heads.

The first models of the 1301 were announced on June 2, 1961. However, the first model of a head per surface disk drive was for the IBM Stretch system at Los Alamos which due to schedule actually required an implementation of the design with pressurized air bearing heds on each disk surface.

Additional information

IBM Archives 1301 Site
IBM San Jose, A Quarter Century Of Innovation”, David W. Kean, 1977, CHM accession number: 102687875
"History of Magnetic Disk Storage Based on Perpendicular Magnetic Recording," A. Hoagland, IEEE Trans Mag, Jul 2003
[Bashe86] Bashe et al, "IBM;s Early Computers," The MIT Press, Cambridge MA, 1986.

Provenance note: This page was originally authored by Al Hoagland; his last approved revision was version 23