IEEE Computer Volume 12 Number 5 -- NEW APPLICATIONS & RECENT RESEARCH
Original Publication Date: 1979-May-01
Included in the Prior Art Database: 2005-Nov-10
Software Patent Institute
Prof. Demetrios Michalopoulos: AUTHOR [+3]
NEW APPLICATIONS & RECENT RESEARCH * Wall encoding quadruples density of bubble device * Computer technology colors basic learning program for handicapped children
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NEW APPLICATIONS & RECENT RESEARCH
Prof. Demetrios Michalopoulos
California State University, Fullerton
Wall encoding quadruples density of bubble device
By the simple tactic of using two distinct types of magnetic bubbles, IBM scientists have increased the information storage density of a conventionally designed magnetic bubble device by a factor of four.
A team headed by Dr. Ta-Lin Hsu of IBM's San Jose Research Laboratory has fabricated and
tested a fully operational experimental device capable of storing 15,000 bubbles at a density of
3.3 million bubbles per square centimeter or 22 milbon bubbles per square inch. This is nearly four times the density that can be achieved using bubbles of the same size.
The experimental device demonstrates a practical method for crossing the socalled one- megabit barrier that currently Emits the storage capacity of magnetic bubble devices. Pushed to its Emits, the conventional technology is capable of storing one milbon bits in a chip one centimeter square. With the approach used in the IBM experiments, conventional fabrication techniques can push the capacity of such chips up to four milbon bits.
As in conventional devices, the microcircuit pattern deposited on the surface of the device described by Dr. Hsu is composed of loops of microscopic permalloy elements, each having the shape of a chevron. Magnetic bubbles can be made to move through the device beneath these chevron elements. In doing this, they pass from one arm of a chevron to the other, and then on to an adjacentchevron, forming streams of continuously circulating bubbles in the device.
The design of the experimental device differs from that of conventional devices in two important ways. First, the chevron elements are half as tall and half as wide as usual; thus four times as many can fit into the same area. Since the gap separating one chevron from its neighbor is kept the same as usual, the fabrication processes can be essentially identical. Second, special encoding and decoding stations are added to the device so that two d fferent types of bubbles can be formed and distinguished from each other. This change is the key to achieving higher storage density.
Conventional magnetic bubble devices use bubbles that are physically indistinguishable from each other. Since information is represented by noting the presence or absence of a bubble at a particular storage location, the device becomes peppered with empty spaces wherever there are zeros in the data. It is these randomly located gaps in an array of bu...