The basics of bubble memory

In the early '80 semiconductor memory was relatively expensive and the alternative, floppy disks or harddisks, too fragile and bulky for some applications.

Therefore Intel (yes, they were in the memory business then) and others looked for alternatives. Bubbles were one of them. It is easiest to see bubble memories as floppies, but only the bits (bubbles) rotate. The medium, or 'disk' is stationary.

The bubble technology was 'preliminary' in 1981 but became obsolete within five years, when battery backup-ed CMOS-RAM became affordable.

The following texts and pictures are from the Intel "Memory Components Handbook Supplement 1984" reprint section.

Picture 1 Magnetic bubble technology A magnetic bubble-memory stores data in the form of cylindrically-shaped magnetic domains in a thin film of magnetic material (The axis of the cylinder is perperdicular to surface of the material. The presence of a domain (a bubble) is interpreted as a binary 1, and absence of a domain is a zero. Bubbles are created from electrical signals by a bubble generator within the memory and reconverted to electrical signals by an internal detector. Externally the memory is TTL-compatible.
Picture 2 Bubble Memory Units An external rotating magnetic field propels bubbles through, the film, metallic patterns, called chevrons, deposited on the film steer the domains in the desired directions. In these respects, magnetic-bubble memories are serial high-density storage devices like electromechanical disk memories. In disks however, the stored bits are stationary on a moving medium, whereas in the magnetic bubble memory the medium is stationary and the bits move.
In the absence of power, the stored bits ( 'bubbles") are held intact by the presence of permanent magnets, contained within the memory's shielded package. Hence the non-volatility of data is assured. More info on the Intel 7110 Functional Description page.
Gespac GESBUL-1 Bubble memory application This is a magnetic bubble memory as found on the Gespac GESBUL-1, a GESBUS-64 system euro-card. It was used as data storage in the Landis & Gyr Bomics work-time registration and access control system. But that is ancient history.

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Latest update: 2002-06-21

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