GB1186703A - Associative Memory - Google Patents

Abstract

1,186,703. Associative stores; computers. INTERNATIONAL BUSINESS MACHINES CORP. 5 Oct., 1967, No. 45432/67. Headings G4A and G4C. In an associative memory, each word store has a plurality of bi-stable devices associated with it, setting of ;any one of which enables a read or write signal subsequently to be applied to the word store, selection means being provided to set a selectable one of the bi-stable devices in response to the generation of a match signal. The associative store of Fig. 1 comprises: an input register 2; a mask register (with gates) 4; logic circuits 6; word stores 7 each bit position being capable of three states viz. 0, 1, nothing; a primary and a secondary trigger 16, 17 respectively (with logic) associated with each word store; an output register 9; and a decoder 19 which can produce any of the following operations: SELECT: those orders of the input register 2 which correspond to orders of the mask register 4 set at 1 are compared with corresponding orders of the word stores 7 (decoder output S energized), match setting either the primary or the secondary trigger (according as decoder output P or SY is energized). SELECT NEXT: like " select " only the primary or secondary trigger of the next word store is set on match, not that of the word store giving the match (decoder output N also energized). TRANSFER TO NEXT: the set state of each set primary or secondary trigger (depending on whether P or SY is energized) is transferred to the next such trigger (N energized). READ: those word stores whose primary or secondary triggers (depending on P or SY) are set are read out to the output register 9 simultaneously (so that if there are a plurality of such word stores corresponding bits are ORed on the column lines 11, 12) and in any event only those positions at which the mask register 4 holds 0 are gated at 71 to the output register 9 (decoder output R energized). WRITE: contents of input register 2 at those orders corresponding to orders of the mask register 4 set at 0 are written into those word stores having the primary or secondary trigger set (depending on P or SY; W also energized). SET MASK: input register 2 loads the mask register 4 (SM energized). SWITCH: output SW of decoder 19 is energized to overrule the selective effects of the mask register 4. Combinations of the above operations are possible. In a computer, accessing of instruction words belonging to the main programme and to subroutines may be controlled by the primary and secondary triggers respectively TRANSFER TO NEXT followed by READ can be used for stepping through a set of consecutive instructions, a branch being initiated by using SWITCH as well.