Content-Addressable and Associative Memory Systems a Survey

This review of content-addressable memory and as-A. Purpose of This Study sociative computer systems represents an attempt to consolidate and report nontechnically the direction in which numerous independent The primary purpose of this study is to provide in-research programs have progressed during the last ten years. The formation bases on which recommendations can be made paper reflects the views of a myriad of researchers on subjects of concerning future efforts in this area. A survey of the organization (configuration concepts), hardware elements, logical literature in the field, as indicated by the voluminous operations, speed, cost, size, software implications, applications, bibliography, provided useful data on hardware, soft-advantages and disadvantages. In a report of this type it is important warappliction,dad usepts on ardware exf to quote directly and indirectly from the researchers themselves, ware, applications, and concepts which are to some ex-so that the trends or directions of their concepts may converge into tent summarized in the following pages. Direct and in-meaningful information. Acknowledgement is made to those quoted direct quotations of the authors are used liberally in (see bibliography references) since they represent the meat of this order to preserve accuracy in the reporting. Comprehen-survey. The bibliography, although voluminous, is not necessarily complete. A number of reference sources may have been overlooked usie te investiatos of the ressing lements inadvertently. It is hoped, however, that the information and the used are left to the resources of the research laboratory. bibliography will serve as a base for those entering into research connected with this rapidly developing concept. II. CONFIGURATION CONCEPTS I. INTRODUCTION Three concepts are emerging from current work in the A SSOCIATIVE memories have been generally de-field: scribed as a collection or assemblage of ele-1) a content-addressable memory, which is used as ments having data storage capabilities, and an extension of a conventionally organized mem-which are accessed simultaneously and in parallel on ory, for the performance of a variety of logical the basis of data content rather than by specific address search and match operations; or location. 2) a content-addressable memory, large enough to A memory, which in one word time finds a matching act as a special purpose primary data storage and segment and reads the remainder of the word, has been retrieval device; and, called by one of these names: Catalog Memory, Associ-3) an "associative" processor, containing a content-ative Memory, Content-Addressed Memory (CAM), addressable memory with cells capable of …