Drum memory

Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. It was widely used in the 1950s and into the 1960s as computer memory.

For many early computers, drum memory formed the main working memory of the computer. It was so common that these computers were often referred to as drum machines. Some drum memories were also used as secondary storage.

Drums were displaced as primary computer memory by magnetic core memory which was faster (no moving parts), less expensive and more dense. Similarly, drums were replaced by hard disk drives for secondary storage, which were also less expensive and more dense. The manufacture of drums ceased in the 1970s.

Design

A drum memory contained a large metal cylinder, coated on the outside surface with a ferromagnetic recording material. It could be considered the precursor to the hard disk drive (HDD), but in the form of a drum rather than a flat disk. In most designs, one or more rows of fixed read-write heads ran along the long axis of the drum, one for each track. The drum's controller simply selected the proper head and waited for the data to appear under it as the drum turned (rotational latency). Not all drum units were designed with each track having its own head. Some, such as the English Electric DEUCE drum and the Univac FASTRAND had multiple heads moving a short distance on the drum in contrast to modern HDDs, which have one head per platter surface.