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Early type of computer external data storage From Wikipedia, the free encyclopedia
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]
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 eight 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 replaceable.[1]
The magnetic tape is a 5/8-inch (1.6 cm) wide and 0.05 mm thick Mylar 3M Co type 188.[3]: 11 The 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 three-phase 380 volts 50 Hz with 300 W when in standby and 750 W when active. Signaling for data uses eight parallel -20 V to 0 V 5 μs pulses.[3]: 13
Peak transfer speed is 182,044 bits/s,[3][4] using eight parallel lines[3]: 13 and thus 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.[5]
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