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Error Detection and Accommodation in Magnetic Bubble Storage Loops

IP.com Disclosure Number: IPCOM000081044D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Chang, H: AUTHOR [+3]

Abstract

Magnetic bubble storage loops employ an overlay of permalloy patterns to guide a recirculating bubble stream, pulsed to travel over one site at every bit-time. However, the overlay or the storage medium may contain defects such that bubbles (considered to be 1's) are trapped. On a one-hundred thousand bit loop (such as used in dynamically order shift registers), one or two such defects are conceivable. These defects, as formed during manufacturing, do not change with time.

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Error Detection and Accommodation in Magnetic Bubble Storage Loops

Magnetic bubble storage loops employ an overlay of permalloy patterns to guide a recirculating bubble stream, pulsed to travel over one site at every bit- time. However, the overlay or the storage medium may contain defects such that bubbles (considered to be 1's) are trapped. On a one-hundred thousand bit loop (such as used in dynamically order shift registers), one or two such defects are conceivable. These defects, as formed during manufacturing, do not change with time.

Rather than rejecting a defective loop, it is vastly more rewarding to use it as a loop of slightly lower capacity. This problem is solved by: a) a procedure for sensing defects; and b) a mechanism to make a defective loop behave as a normal loop in capacity and in traversal time.

A permalloy defect in a storage loop presents inadequate magnetization, in response to one of the (3 or 4) phases of the rotation magnetic field. It permits the passage of a vacancy (a 0), but has inadequate strength to guide a bubble (a
1). Thus, a lone bubble in an otherwise vacant stream encountering a "fresh" fault (i.e., one that has not encountered a bubble before) will be trapped; the output from the fault would be a perfectly vacant stream.

The trapped bubble can be released if another bubble comes from behind to furnish enough mutual repulsion; then the old bubble leaves the fault as the new one becomes trapped. It thus looks as if the new bubble has jumped over the fault, moving over two sites in one bit-time.

Most permalloy defects have a predictable behavior; namely, it will trap a bubble and will release the latter if and only if another bubble comes along ready to be trapped. The predictability is traceable to the fact that the bubbles i...