A look at the core memory module from a 1980 Spacelab computer

Spacelab's Computer System

Spacelab, a reusable laboratory carried by the Space Shuttle, utilized a French-built minicomputer, the Mitra 125 MS, for its operations. This choice differed from the Shuttle's main IBM-built AP-101 systems, reflecting Spacelab's European origins. Three Mitra computers were onboard: one for Spacelab management, one for experiment control, and a third as a backup.

Magnetic Core Memory in Detail

The Mitra 125 MS computer featured 128 kilobytes of RAM, implemented using magnetic core memory rather than silicon. This storage method involved storing each bit in a small ferrite ring. The core memory stack, which occupied about a third of the computer's volume, was designed to slide out for maintenance.

Physical Configuration and Cooling

The core memory stack comprised seven boards: two driver boards, four core plane boards, and an interface board. These boards connected to large daughter boards via 160-pin connectors, which then linked the memory stack to the rest of the computer. The system was cooled by conduction, with the core memory stack firmly attached to a detachable side panel of the computer to dissipate heat.

Historical Context of Core Memory

Magnetic core memory addressed the storage challenges faced by early computers in the mid-20th century. Prior methods like sound waves in mercury or CRT spots had limitations. The development of special magnetic alloys during World War II, capable of flipping between magnetic states, provided a foundation for creating dense, reliable, and randomly accessible binary data storage.