Carousel memory is a type of

secondary storage Computer data storage or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The cent ...

for computers, which was created by Swedish computer engineers and Gunnar Stenudd. It was first shown at an exhibition in

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

in 1958.

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 Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic ...

, it instead has 64 small rolls of each, with wide tape on each roll, divided into per roll. The tape speed is . 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 and the storage space is . The control system is operated by

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

s. 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 BoPET (biaxially oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical stability, dimensional stability, transparency reflectivity, an ...

3M Co type 188.The storage density is specified to , and the access head is capable of simultaneous read/write operations. The power requirement is three-phase 380 volts 50 Hz with when in standby and when active. Signaling for data uses eight parallel -20 V to 0 V 5 μs pulses. Peak transfer speed is , using eight parallel lines and thus per line. The first delivery of the Facit EDB 3 computer was in 1958 (to ASEA in

Västerås Västerås () is a city in central Sweden on the shore of Mälaren, Lake Mälaren in the province of Västmanland, west of Stockholm. The city had a population of 127,799 at the end of 2019, out of the municipal total of 158,653, over 100,000 mo ...

) used the carousel memory Facit ECM 64.

Description

See also

References

Further reading