Carousel memory

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 {{nowrap|9 meters}} each, with {{nowrap|1.6-cm}} wide tape on each roll, divided into {{nowrap|eight channels}} per roll.{{Citation|title=TPU 610301 FACIT ECM 64 Karusellminne, Preliminär teknisk beskrivning|date=1961|url=http://www.tekniskamuseet.se/download/18.4d755928124885167d48000388/1339755649132/TM39138Bil3_+FacitECM64_+karusellminne_+prelteknisk+beskrivning.pdf|publication-date=2012-06-15|author=FACIT electronics AB|page=3|publisher=Swedish National Museum of Science and Technology|language=sv|trans-title=TPU 610301 FACIT ECM 64 Carousel memory, preliminary technical description|url-status=dead|archive-url=https://web.archive.org/web/20161013091854/http://www.tekniskamuseet.se/download/18.4d755928124885167d48000388/1339755649132/TM39138Bil3_%2BFacitECM64_%2Bkarusellminne_%2Bprelteknisk%2Bbeskrivning.pdf|archive-date=2016-10-13}}{{rp|3}} The tape speed is {{nowrap|5 m/s}}.{{rp|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 {{nowrap|2 seconds}}{{rp|11}} and the storage space is {{nowrap|2560 kilobytes}}.{{Citation |author=FACIT electronics AB |date=1963 |publication-date=2012-06-15 |title=Facit Electronic presenterar FACIT ECM 64 Magnetbandsminne av karuselltyp med direkt access |trans-title=Facit Electronics presents FACIT ECM 64 Magnetic tape memory of carousel type with direct access |url=http://www.tekniskamuseet.se/download/18.4d755928124885167d48000387/1339755649101/TM39138Bil1_FacitECM64_broschyr-+Magnetbandsminneavkaruselltypmeddirektaccess.pdf |publisher=Swedish National Museum of Science and Technology |language=sv |url-status=dead |archive-url=https://web.archive.org/web/20161013091952/http://www.tekniskamuseet.se/download/18.4d755928124885167d48000387/1339755649101/TM39138Bil1_FacitECM64_broschyr-%2BMagnetbandsminneavkaruselltypmeddirektaccess.pdf |archive-date=2016-10-13 }} The control system is operated by transistors. Both the carousel and individual spools are replaceable.

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

Peak transfer speed is {{nowrap|182,044 bits/s}}, using eight parallel lines{{rp|13}} and thus {{nowrap|22,756 bits/s}} per line.

The first delivery of the Facit EDB 3 computer was in 1958 (to ASEA in Västerås) used the carousel memory Facit ECM 64.{{Citation|author=Arvidsson, Göran |date=2002 |publication-date=2015-08-23 |title=FACIT i den tidiga dataåldern |trans-title=FACIT in the early computer age |pages=3 |url=http://www.brukskultur.se/uploadedFiles/81_data.pdf |language=sv }}

• BESK, Sweden's first electronic computer, also developed by Erik Stemme
• Exatron Stringy Floppy, 1978 endless tape drive
• Karlqvist gap, calculation of magnetic field in ferromagnetic layer
• Rotronics Wafadrive, 1984 endless tape drive
• ZX Microdrive, 1983 endless tape drive

• {{Citation|title=Applications to the magnetic tape storage unit, facit ECM64 (the Carousel Memory)|journal=BIT Numerical Mathematics | date=March 1962 | volume=2 | issue=1 | pages=16–20 |doi=10.1007/BF02024778 |last1=Karlqvist |first1=Olle }}

{{Magnetic tape data formats}}

Category:Information technology in Sweden

Category:Swedish inventions