Carousel memory

Carousel memory Facit ECM 64 from Facit (2010)
Carousel memory for SMIL, now at the "Teknikens och sjöfartens hus" in Malmö, Sweden (2013)

Carousel memory is a type of secondary storage for computers, which was created by Swedish computer engineers Erik Stemme and Gunnar Stenudd.[1] It was first shown at an exhibition in Paris in 1958.[2]

Description

The FACIT ECM 64, manufactured by Swedish company Facit AB, is a prototype of carousel memory. To avoid having a single, long magnetic tape, it instead has 64 small rolls of 9 meters each, with 1.6-cm wide tape on each roll, divided into 8 channels per roll.[3]:3 The tape speed is 5 m/s.[3]:6 To read a particular roll, the carousel rotates so the desired roll ends up at the bottom. A counterweight sits at the free end of the tape, and facilitates the roll in moving out and down into a mechanism with a read-and-write head. The tape is then rewound. The average seek time is 2 seconds[3]:11 and the storage space is 2560 kilobytes.[4] The control system is operated by transistors. Both the carousel and individual spools are replicable.[1]

The magnetic tape is a 5/8-inch (1.6 cm) wide and 0.05 mm thick Mylar 3M Co type 188.[3]:11The storage density is specified to 8 bits/mm,[3]:4 and the access head is capable of simultaneous read/write operations.[3]:3 The power requirement is 3-phase 380 volts 50 Hz, with 300 W when in standby and 750 W when active. Signaling for data uses 8 parallel -20 V to 0 V 5 µs pulses.[3]:13

Peak transfer speed is 182,044 bits/s,[3][4] using 8-parallel lines[3]:13 and thus 22,756 bits/s per line.

The first delivery of the Facit EDB 3 computer in 1958 (to ASEA in Västerås) used the carousel memory Facit ECM 64.[5]

See also

References

  1. 1 2 Pär Rittsel (2002), Valsen inledde skivans historia [The roll initiated the disc history] (in Swedish), International Data Group (published 2010-09-11), retrieved 2016-03-22
  2. ↑ Magnetband till karusellminne, Föremål [Magnetic tape for carousel memory, Object] (in Swedish), Kringla, Riksantikvarieämbetet, retrieved 2016-03-22
  3. 1 2 3 4 5 6 7 8 9 FACIT electronics AB (1961), TPU 610301 FACIT ECM 64 Karusellminne, Preliminär teknisk beskrivning [TPU 610301 FACIT ECM 64 Carousel memory, preliminary technical description] (PDF) (in Swedish), Swedish National Museum of Science and Technology (published 2012-06-15), p. 3, archived from the original (PDF) on 2016-10-13
  4. 1 2 FACIT electronics AB (1963), Facit Electronic presenterar FACIT ECM 64 Magnetbandsminne av karuselltyp med direkt access [Facit Electronics presents FACIT ECM 64 Magnetic tape memory of carousel type with direct access] (PDF) (in Swedish), Swedish National Museum of Science and Technology (published 2012-06-15), archived from the original (PDF) on 2016-10-13
  5. ↑ Arvidsson, Göran (2002), FACIT i den tidiga dataåldern [FACIT in the early computer age] (PDF) (in Swedish) (published 2015-08-23), p. 3

Further reading

  • "Applications to the magnetic tape storage unit, facit ECM64 (the Carousel Memory)" (PDF), BIT Numerical Mathematics, 2 (1), pp. 16–20, March 1962
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