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Content-addressable memory

Content-addressable memory (CAM) is a special type of computer memory used in certain very-high-speed searching applications. It is also known as associative memory or associative storage and compares input search data against a table of stored data, and returns the address of matching data.[1]

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The data word recognition unit was proposed by Dudley Allen Buck in 1955.[2]

CAM is frequently used in networking devices where it speeds forwarding information base and routing table operations.

Contents 1 Hardware associative array 2 Standards 3 Semiconductor implementations 4 Alternative implementations 5 Ternary CAMs 6 Example applications 7 See also 8 References 9 Bibliography 10 External links Hardware associative array Unlike standard computer memory, random access memory (RAM), in which the user supplies a memory address and the RAM returns the data word stored at that address, a CAM is designed such that the user supplies a data word and the CAM searches its entire memory to see if that data word is stored anywhere in it. If the data word is found, the CAM returns a list of one or more storage addresses where the word was found. Thus, a CAM is the hardware embodiment of what in software terms would be called an associative array.[3]

Standards A major interface definition for CAMs and other network search engines (NSEs) was specified in an interoperability agreement called the Look-Aside Interface (LA-1 and LA-1B) developed by the Network Processing Forum, which later merged with the Optical Internetworking Forum (OIF). Numerous devices conforming to the interoperability agreement have been produced by Integrated Device Technology, Cypress Semiconductor, IBM, Broadcom and others. On December 11, 2007, the OIF published the serial lookaside (SLA) interface agreement.