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Gated Search Read Associative Array Logic Module

IP.com Disclosure Number: IPCOM000076474D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 4 page(s) / 62K

Publishing Venue

IBM

Related People

DasGupta, S: AUTHOR [+2]

Abstract

Functional Memory is a general purpose systems technology which has been proposed as a solution to the problems of large-scale integration. The problems of large-scale integration have been stated many times, and need not be repeated here. Because of these problems, the following properties are desirable for a logic module made in large-scale integration: 1) high-circuit density, 2) regularity of interconnections between circuits, 3) high circuit-to-edge connector ratio, 4) loadable, i.e., have easily changeable personality; this is to ensure high usage of module type, 5) easily testable.

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Gated Search Read Associative Array Logic Module

Functional Memory is a general purpose systems technology which has been proposed as a solution to the problems of large-scale integration. The problems of large-scale integration have been stated many times, and need not be repeated here. Because of these problems, the following properties are desirable for a logic module made in large-scale integration:
1) high-circuit density,
2) regularity of interconnections between

circuits,
3) high circuit-to-edge connector ratio,
4) loadable, i.e., have easily changeable

personality; this is to ensure high usage

of module type,
5) easily testable.

The circuit organization that fits these requirements best is a storage array. Functional memory attempts to solve the problems of large-scale integration by using a storage array to perform logic economically.

The functional memory module can be used either as a logic store control store, associative store, or logic block. In its use as a logic block, logic is performed by associative table look-up, using the DON'T CARE state to give significant compression of tables over conventional two state arrays (typically n to n2 words for functional memory instead of 2n words for conventional two state arrays).

The background of functional memory and the associative array module is described in the article "Functional Memory and Its Micro Programming Implications", by Peter L. Gardner, IBM, United Kingdom Laboratories, Ltd., Winchester, Hants, England, IEEE Transactions on Computers, Volume C-2O, No. 7 July 1971 pp. 764-775.

The present system involves a modification of associative array logic. The principle of a functional memory (array logic) look-up table is to present a search argument to a table stored in an array of storage cells, Dot-OR the results of the matching words and read the final result out. Essentially, the search operation is an AND function between the stored search information and search arguments. Hence, the entire search field can be replaced by hard-wired AND gates, thus causing considerable saving in circuits and, consequently, power and chip size. Besides, the resulting simplification of the data path will improve upon the cycle time of the array logic module.

With given hard-wired AND gates for the search operation, it is necessary to generate the result fields to fit the given gated search scheme. Hence, any final design will have to include an optimal hard-wired gate scheme and an optimal result field generation.

Hard-wired decoders, like those used in random-access memories, have the capability of selecting only one word since each word is powered by an AND gate

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in the decoder with unique inputs. For example, a decoder with three inputs A, B, C has 2/3/ = 8 unique outputs ABC, ABC, ABC, ABC, ABC, ABC, ABC, ABC. However, if the inputs are grouped in pairs, then the decoder could have 12 outputs - AB, AB, AB, AB, BC, BC, BC, BC, CA, CA, CA, CA - none of which are un...