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Bubble memory
Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles or domains, each storing one bit of data. The material is arranged to form a series of parallel tracks that the bubbles can move along under the action of an external magnetic field. The bubbles are read by moving them to the edge of the material, where they can be read by a conventional magnetic pickup, and then rewritten on the far edge to keep the memory cycling through the material. In operation, bubble memories are similar to delay-line memory systems.
Bubble memory started out as a promising technology in the 1970s, offering performance similar to core memory, memory density similar to hard drives, and no moving parts. This led many to consider it a contender for a "universal memory" that could be used for all storage needs. The introduction of dramatically faster semiconductor memory chips in the early 1970s pushed bubble into the slow end of the scale and it began to be considered mostly as a replacement for disks. The equally dramatic improvements in hard-drive capacity through the early 1980s made it uncompetitive in price terms for mass storage.
Bubble memory was used for some time in the 1970s and 1980s in applications where its non-moving nature was desirable for maintenance or shock-proofing reasons. The introduction of flash storage and similar technologies rendered even this niche uncompetitive, and bubble disappeared entirely by the late 1980s.
Bubble memory is largely the brainchild of a single person, Andrew Bobeck. Bobeck had worked on many kinds of magnetics-related projects through the 1960s, and two of his projects put him in a particularly good position for the development of bubble memory. The first was the development of the first magnetic-core memory system driven by a transistor-based controller, and the second was the development of twistor memory.
Twistor memory is essentially a version of core memory that replaces the "cores" with pieces of magnetic tape. The main advantage of twistor memory is its ability to be assembled by automated machines, as opposed to core memory, which was almost entirely manually assembled. AT&T had great hopes for twistor memory, believing that it would greatly reduce the cost of computer memory and put them in an industry leading position. Instead, DRAM memories came onto the market in the early 1970s and rapidly replaced all previous random-access memory systems. Twistor memory ended up being used only in a few applications, many of them AT&T's own computers.
One interesting side effect of the twistor concept was noticed in production: under certain conditions, passing a current through one of the electrical wires running inside the tape would cause the magnetic fields on the tape to move in the direction of the current. If used properly, it allowed the stored bits to be pushed down the tape and pop off the end, forming a type of delay-line memory, but one where the propagation of the fields was under computer control, as opposed to automatically advancing at a set rate defined by the materials used. However, such a system had few advantages over twistor memory, especially as it did not allow random access.
In 1967, Bobeck joined a team at Bell Labs and started work on improving twistor memory. The memory density of twistor memory was a function of the size of the wires; the length of any one wire determined how many bits it held, and many such wires were laid side-by-side to produce a larger memory system.
Conventional magnetic materials, like the magnetic tape used in twistor memory, allowed the magnetic signal to be placed at any location and to move in any direction. Paul Charles Michaelis working with permalloy magnetic thin films discovered that it was possible to move magnetic signals in orthogonal directions within the film. This seminal work led to a patent application. The memory device and method of propagation were described in a paper presented at the 13th Annual Conference on Magnetism and Magnetic Materials, Boston, Massachusetts, 15 September 1967. The device used anisotropic thin magnetic films that required different magnetic pulse combinations for orthogonal propagation directions. The propagation velocity was also dependent on the hard and easy magnetic axes. This difference suggested that an isotropic magnetic medium would be desirable.
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Bubble memory AI simulator
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Bubble memory
Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles or domains, each storing one bit of data. The material is arranged to form a series of parallel tracks that the bubbles can move along under the action of an external magnetic field. The bubbles are read by moving them to the edge of the material, where they can be read by a conventional magnetic pickup, and then rewritten on the far edge to keep the memory cycling through the material. In operation, bubble memories are similar to delay-line memory systems.
Bubble memory started out as a promising technology in the 1970s, offering performance similar to core memory, memory density similar to hard drives, and no moving parts. This led many to consider it a contender for a "universal memory" that could be used for all storage needs. The introduction of dramatically faster semiconductor memory chips in the early 1970s pushed bubble into the slow end of the scale and it began to be considered mostly as a replacement for disks. The equally dramatic improvements in hard-drive capacity through the early 1980s made it uncompetitive in price terms for mass storage.
Bubble memory was used for some time in the 1970s and 1980s in applications where its non-moving nature was desirable for maintenance or shock-proofing reasons. The introduction of flash storage and similar technologies rendered even this niche uncompetitive, and bubble disappeared entirely by the late 1980s.
Bubble memory is largely the brainchild of a single person, Andrew Bobeck. Bobeck had worked on many kinds of magnetics-related projects through the 1960s, and two of his projects put him in a particularly good position for the development of bubble memory. The first was the development of the first magnetic-core memory system driven by a transistor-based controller, and the second was the development of twistor memory.
Twistor memory is essentially a version of core memory that replaces the "cores" with pieces of magnetic tape. The main advantage of twistor memory is its ability to be assembled by automated machines, as opposed to core memory, which was almost entirely manually assembled. AT&T had great hopes for twistor memory, believing that it would greatly reduce the cost of computer memory and put them in an industry leading position. Instead, DRAM memories came onto the market in the early 1970s and rapidly replaced all previous random-access memory systems. Twistor memory ended up being used only in a few applications, many of them AT&T's own computers.
One interesting side effect of the twistor concept was noticed in production: under certain conditions, passing a current through one of the electrical wires running inside the tape would cause the magnetic fields on the tape to move in the direction of the current. If used properly, it allowed the stored bits to be pushed down the tape and pop off the end, forming a type of delay-line memory, but one where the propagation of the fields was under computer control, as opposed to automatically advancing at a set rate defined by the materials used. However, such a system had few advantages over twistor memory, especially as it did not allow random access.
In 1967, Bobeck joined a team at Bell Labs and started work on improving twistor memory. The memory density of twistor memory was a function of the size of the wires; the length of any one wire determined how many bits it held, and many such wires were laid side-by-side to produce a larger memory system.
Conventional magnetic materials, like the magnetic tape used in twistor memory, allowed the magnetic signal to be placed at any location and to move in any direction. Paul Charles Michaelis working with permalloy magnetic thin films discovered that it was possible to move magnetic signals in orthogonal directions within the film. This seminal work led to a patent application. The memory device and method of propagation were described in a paper presented at the 13th Annual Conference on Magnetism and Magnetic Materials, Boston, Massachusetts, 15 September 1967. The device used anisotropic thin magnetic films that required different magnetic pulse combinations for orthogonal propagation directions. The propagation velocity was also dependent on the hard and easy magnetic axes. This difference suggested that an isotropic magnetic medium would be desirable.