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Browse Prior Art Database

Comparing Technique

IP.com Disclosure Number: IPCOM000094523D
Original Publication Date: 1965-Feb-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Scott, TR: AUTHOR

Abstract

Two locations in a memory can be compared by simultaneously reading them out to the sense amplifiers, if the two words were previously stored in complementarily opposite unipolar modes.

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Comparing Technique

Two locations in a memory can be compared by simultaneously reading them out to the sense amplifiers, if the two words were previously stored in complementarily opposite unipolar modes.

Certain memories are capable of operation in two oppositely polarized unipolar modes. In such memories, it is usual to choose one unipolar mode, such as positive 1's and operate within that mode only, with 0 bits providing zero signals and 1 bits providing positive polarity outputs. The other unipolar mode, negative 1's, in such case is not used.

Comparing in memory is possible by storing a test word in the otherwise unused unipolar mode and reading the test word out along with the selected word to be tested. If there is a perfect match, the negative 1's and positive 1's are arranged to buck and cancel, and the 0 signals cancel, at the sense amplifiers. If there is anything other than a perfect match, either a negative polarity signal output from the test word or a positive signal output from the selected word remains uncancelled. Such a signal indicates inequality of the test word to the selected word.

Certain nondestructive readout, magnetic film memories and multiaperture core memories are capable of operation in the requisite complementary unipolar modes. Storing certain test words in the unipolar mode opposite to the unipolar mode used for general storage permits comparing in memory. This is effected simply by reading out the test word with a selected gene...