IBM 1301 DISK DRIVE

The 1301 disk drive was the disk drive that followed the RAMAC.The Advanced Disk File (ADF) was initiated in 1955 on the basis of performance requirements essential to maintain and expand the role of disk drives based on a rotating disk stack. These included a far faster access time (already available with magnetic drum devices) and much larger capacity at a much lower cost per byte, that a drum configuration could not provide. The design thus included a head per surface and a greatly increased storage density, both features dependent on requiring flying heads that did not require a compressed air source and were able to be spaced much closer to the disk surfaces, The flying head and the continual advances it offered in closer spacings has been the essential driving factor in disk magnetic fisk technology ever since. The 1301 design 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 transaction processing set of applications that the 1301 targeted.

The ADF (Advanced Disk File) in 1955 was based on a a flying head per surface initially chose perpendiular ecording usung probe heads and oxidized steel disks (well before the RAMAC was announced). A January 1960 audit concluded that the three new technologies it incorporated

1. Flying heads
2. A high-speed high accuracy hydraulic acyuator to move the large "comb" array of magnetic heads
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 the ADF 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 that Jake Hagopian demonstrated to everyone in the laboratory.

A team inder Jack Harker did the fundamental research to define the slider bearing contours need for flying on spinning thin flat disk surfaces, a much more challenging task then needed to the use of rotating drum surfaces.

The first models of the 1301 were announced on June 2, 1961. For the same number of and size of disks as used on the RAMAC the capacity was ten times as great and the access time greaer by a factor of 4 to 5.
Additional information

IBM 1301
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.

A.S. Hoagland