08-02-2010, 10:20 PM
please read this
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, associative storage Unlike standard computer memory (random access memory or 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, Because a CAM is designed to search its entire memory in a single operation, it is much faster than RAM in virtually all search applications. , There are cost disadvantages to CAM however. Unlike a RAM chip, which has simple storage cells, each individual memory bit in a fully parallel CAM must have its own associated comparison circuit to detect a match between the stored bit and the input bit. Additionally, match outputs from each cell in the data word must be combined to yield a complete data word match signal. The additional circuitry increases the physical size of the CAM chip which increases manufacturing cost. The extra circuitry also increases power dissipation since every comparison circuit is active on every clock cycle. Consequently, CAM is only used in specialized applications where searching speed cannot be accomplished using a less costly method. And content addressable memory is using comparison logic with each bit of storage. A data value is broadcast to all words of storage and compared with the values there. Words which match are flagged in some way. Subsequent operations can then work on flagged words, e.g. read them out one at a time or write to certain bit positions in all of them. A CAM can thus operate as a data parallel (SIMD) processor , Writing to a CAM is exactly like writing to a conventional RAM. However, the read operation is actually a search of the CAM for a match to an input "tag." In addition to storage cells, the CAM requires one or more comparators
For more please visit
http://en.wikipediawiki/Content-addressable_memory
http://citeseerx.ist.psu.edu/viewdoc/dow...1&type=pdf
http://acteldocuments/CAM_AN.pdf
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, associative storage Unlike standard computer memory (random access memory or 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, Because a CAM is designed to search its entire memory in a single operation, it is much faster than RAM in virtually all search applications. , There are cost disadvantages to CAM however. Unlike a RAM chip, which has simple storage cells, each individual memory bit in a fully parallel CAM must have its own associated comparison circuit to detect a match between the stored bit and the input bit. Additionally, match outputs from each cell in the data word must be combined to yield a complete data word match signal. The additional circuitry increases the physical size of the CAM chip which increases manufacturing cost. The extra circuitry also increases power dissipation since every comparison circuit is active on every clock cycle. Consequently, CAM is only used in specialized applications where searching speed cannot be accomplished using a less costly method. And content addressable memory is using comparison logic with each bit of storage. A data value is broadcast to all words of storage and compared with the values there. Words which match are flagged in some way. Subsequent operations can then work on flagged words, e.g. read them out one at a time or write to certain bit positions in all of them. A CAM can thus operate as a data parallel (SIMD) processor , Writing to a CAM is exactly like writing to a conventional RAM. However, the read operation is actually a search of the CAM for a match to an input "tag." In addition to storage cells, the CAM requires one or more comparators
For more please visit
http://en.wikipediawiki/Content-addressable_memory
http://citeseerx.ist.psu.edu/viewdoc/dow...1&type=pdf
http://acteldocuments/CAM_AN.pdf
