Design Techniques of a Delay-Line Content-Addressed Memory

This paper describes a word-organized concept for retrieving information by means of word association which can be queried in, at most, one ``access´´ time. An example of a 1000-word content-addressed memory (CAM) organization is given. It is shown that for a relatively simple logic organization worst-case word association times of 10 ¿s¿and even faster¿are possible. The memory organization for simple equality, pseudo-parallel equality, and between-limits searches is illustrated and discussed. These memory systems require the use of wide-band ultrasonic delay lines (using the most recent advances in ultrasonics, and not commercially available) and high speed (100-200 Mc/s) digital logic. The design, fabrication, and application of the parameters of these delay lines are discussed, based on experimental results achieved at Lockheed Electronics. The delay-line memory system can be both location-and-content-addressable, and has several advantages over the more common content-addressed (i. e., magnetic and cryogenic) memory systems. The systems described require little power and are physically small and lightweight.