Mainframe Computer Component, Whirlwind Magnetic Core Memory Plane

Mainframe Computer Component, Whirlwind Magnetic Core Memory Plane

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When researchers at the Massachusetts Institute of Technology (MIT) were developing a high-speed, real-time digital computer in the 1940s, they began by using electrostatic tubes to store information. The tubes were delicate and broke down often. MIT’s Whirlwind Computer Project needed a reliable form of information storage for the computer they were building for Cold War-era air defense. The solution – developed by professor Jay W. Forrester and his graduate student Bill Papian in the late 1940s and early 1950s – was a technology called “coincident current ferrite core memory,” or core memory. It stored information in tiny, beadlike ferrite cores strung on a grid of copper wires. Each core stored one bit of information in binary code: encoding a 1 or a 0 through a change in magnetic polarity.
This artifact is a plane of coincident current ferrite core memory. It provided the internal storage for the Whirlwind Computer Project, the first computer to use coincident current core memory. This plane contains 1024 cores, suspended at the meeting of 32 vertical and 32 horizontal copper wires, called “address” wires. Each core is also threaded with a third copper wire, called a “sense” wire, that runs diagonally along the plane. Women working as laboratory assistants at MIT strung the cores and wires by hand. A 64-by-64 core plane could take up to two weeks for the assistants to manufacture. The cores were loaded in batches on to the vertical wires using a needle. Then, they were strung individually with the horizontal wire, one row at a time. The assistants had to carefully alternate the direction from which they entered the core (over or under), creating the dense diamond pattern. By the mid-1950s, the introduction of plastic frames to position the cores helped reduce the total production time for a plane from two weeks to 6 to 8 hours.
Magnetic core memory was the most commonly used type of random-access memory from the mid-1950s to early-1970s, until it was replaced by semiconductor chips. Random-access memory allows for both reading and writing of data. A “read” operation would set all cores to 0, and a “write” operation would set specific cores to 1 or 0 depending on the magnetic polarity of the wires.
Ceruzzi, Paul. A History of Modern Computing (Cambridge, MA: MIT Press, 2003).
Computer Oral History Collection, National Museum of American History Archives
Center, Smithsonian Institution.
Guditz, E. A. and Smith, L.B. (1956). Vacuum and Vibration Speed Assembly of Core
Memory Planes Retrieved from Lincoln Laboratory - Division 6 website:
Monteiro, Stephen. The Fabric of Interface: Mobile Media, Design, and Gender
(Cambridge, MA: The MIT Press, 2017).
Redmond, Kent C. and Thomas M. Smith. From Whirlwind to MITRE: The R&D Story of
the SAGE Air Defense Computer (Cambridge, MA: MIT Press, 2000).
---. Project Whirlwind: A Case History (Bedford, MA: MITRE Corporation, 1975).
Currently not on view
Object Name
Mainframe Component
Massachusetts Institute of Technology. Lincoln Laboratory
overall: 1 1/2 in x 9 1/4 in x 10 1/4 in; 3.81 cm x 23.495 cm x 26.035 cm
ID Number
catalog number
accession number
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Medicine and Science: Computers
Data Source
National Museum of American History
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