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Associative Memory

IP.com Disclosure Number: IPCOM000097652D
Original Publication Date: 1961-Mar-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Rosin, RF: AUTHOR

Abstract

This is a superconductive associative memory which is also effective to interrogate the memory in response to information stored in the memory.

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Associative Memory

This is a superconductive associative memory which is also effective to interrogate the memory in response to information stored in the memory.

Only two storage cells of two words are shown, each of the cells including four cryotrons. Information is stored in each cell in the form of a circulating persistent current, clockwise circulation of this current indicative of a 0 and counterclockwise circulation indicative of a 1.

Information is read into a word by first applying current I in a downward direction for a 0 and in an upward direction for a 1 to each of the word cells. The application of current I to a cell results in its division between a pair of superconducting parallel paths, a first portion flowing through the gate conductor of the write cryotrons K1A, K2A, K1B and K2B. The remaining portion flows through the loop in parallel with it, the current dividing in inverse proportion to the inductance in each path. Next, write current Iw is applied to the selected word. This current switch the gate conductor of the write cryotrons resistive, shifting I entirely into the path in parallel with the gate. The removal of Iw allows the resistive gate to again become superconducting, but I remains entirely in the other parallel path. The removal of I is next effective to establish a circulating persistent current about the superconducting loop formed by the parallel paths, the direction of which is indicative of the information stored.

Readout of information is accomplished by a pair of sense lines S1 and S2 for each column together with a read current IR applied to the row storing the selected word, by way of example, word A. Current along lines S1 normally flows through the gate conductor of K3A, K3B, K4A, K4B and current along lines S2 normally flows through the gate conductors of K5A, K5B, K6A, K6B. However, with a 0 in storage, the magnetic fields generated by IR flowing through a first control of K3A, K4A and the persistent current flowing through a second control are additive. The sum is sufficient to switch the associated gate resistive, shifting currents S1 directly to ground thru K7, K8, etc. Conversely, the magnetic fields generated by IR flowing through a first control of K5A, K6A, etc., and the persistent current representing a 0 flowing through a second control are subtractive, the net sum being essentially zero. This allows the associated gate to remain superconducting and permits S2 to flow....