Content-addressable memory (CAM) is a particular sort of computer memory used in certain very-high-velocity looking out functions. It is also referred to as associative memory or associative storage and compares enter search knowledge against a table of saved information, and returns the tackle of matching knowledge. CAM is ceaselessly used in networking gadgets where it speeds up forwarding information base and Memory Wave routing table operations. This kind of associative memory can be utilized in cache memory. In associative cache memory, both deal with and content is saved aspect by facet. When the handle matches, the corresponding content material is fetched from cache memory. Dudley Allen Buck invented the idea of content-addressable memory in 1955. Buck is credited with the idea of recognition unit. In contrast to standard pc memory, random-entry memory (RAM), during which the person provides a memory address and the RAM returns the info phrase saved at that handle, a CAM is designed such that the person provides a knowledge word and the CAM searches its total memory to see if that information word is saved anywhere in it.

If the data word is found, the CAM returns a list of one or more storage addresses the place the word was found. Thus, a CAM is the hardware embodiment of what in software program terms can be known as an associative array. A significant interface definition for CAMs and other MemoryWave Community serps was specified in an interoperability agreement referred to as the Look-Apart Interface (LA-1 and LA-1B) developed by the Community Processing Discussion board. Numerous units conforming to the interoperability settlement have been produced by Integrated System Expertise, Cypress Semiconductor, IBM, Broadcom and others. On December 11, 2007, the OIF printed the serial look-aside (SLA) interface agreement. CAM is much faster than RAM in information search functions. There are value disadvantages to CAM, however. In contrast to a RAM chip, which has easy storage cells, each individual memory bit in a totally parallel CAM must have its own associated comparability circuit to detect a match between the saved bit and the input bit. Moreover, match outputs from each cell in the information word should be mixed to yield an entire information phrase match sign.

The extra circuitry increases the bodily dimension and manufacturing price of the CAM chip. The additional circuitry also will increase energy dissipation since each comparison circuit is lively on each clock cycle. Consequently, CAM is used solely in specialized functions the place searching velocity cannot be achieved using a much less costly method. One profitable early implementation was a Normal Function Associative Processor IC and System. MOSAID introduced CAM products focusing on networking purposes. These merchandise had been labelled Network Serps (NSE), Community Search Accelerators (NSA), and Information-based mostly Processors (KBP) but were primarily CAM with specialised interfaces and options optimized for networking. At the moment Broadcom gives a number of households of KBPs. To achieve a unique steadiness between velocity, memory measurement and price, some implementations emulate the operate of CAM through the use of standard tree search or hashing designs in hardware, using hardware tips like replication or pipelining to speed up effective efficiency. These designs are often utilized in routers. The Luleå algorithm is an efficient implementation for longest prefix match searches as required in web routing tables.

X or don't care for one or more bits in the stored phrase, MemoryWave Community thus including flexibility to the search. For instance, a saved word of 10XX0 in a ternary CAM will match any of the four search words 10000, 10010, 10100, or 10110. The added search flexibility comes at a further price over binary CAM as the inner memory cell should now encode three doable states instead of the 2 for the binary CAM. This further state is usually carried out by adding a mask bit (care or don't care bit) to every memory cell. In 2013, IBM fabricated a nonvolatile TCAM using 2-transistor/2-resistive-storage (2T-2R) cells. A design of TCAM using hybrid Ferroelectric FeFET was recently published by a group of International scientists. Content material-addressable memory is commonly used in pc networking devices. For instance, when a network change receives an information frame from considered one of its ports, it updates an inner table with the frame's supply MAC tackle and the port it was received on.