Columbia University Computing History   

IBM 2301 Drum Storage

IBM 2301 Drum Storage
Photo: Introduction to IBM Data Processing Systems, IBM Textbook C20-1684, 1968.
The IBM 2301 fixed-head disk, or "drum", late 1960s. The drum is a spinning cylinder with many circular tracks and each track has its own read/write head, so the head don't have to move. The access time, therefore, was significantly faster than a moving-head disk, but the capacity much smaller. Drums were often used as main memory in the 1940s and 50s. By the 1960s they were used mainly for swapping and paging (as, for example, in our 1975-era Digital Equipment Corporation PDP-11/50).

The IBM 2301 had a capacity of 4MB, average access time of 8.6msec, data transfer rate of 1.2MB/sec, and cost about $80,000.[1]

  1. IBM 2301 Drum Storage Unit,, accessed 31 March 2021.
  2. Drum memory, Wikipedia, accessed 31 March 2021.

Columbia University Computing History Frank da Cruz / [email protected] This page created: January 2001 Last update: 31 March 2021