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ISSI fields CAM chip, preps search algorithms

Posted: 26 Feb 2003 ?? ?Print Version ?Bookmark and Share

Keywords:integrated silicon solutions? issi? cam chip? is51vv4064? content addressable memory?

As part of its plan to expand into products outside of memory chips, Integrated Silicon Solutions Inc. (ISSI) has unveiled a unique content-addressable memory (CAM) technology that can search for multiple packet addresses simultaneously.

At the same time, the company said it is preparing to offer search algorithms that would work with standard memory chips as an alternative to more expensive CAM chips.

The CAM technology, developed by a group of engineers ISSI acquired when it bought Purple Ray Inc. one year ago, is based on an array of smaller CAM "tiles," building blocks that can be used to configure search engines with different widths and depths. One tile has 1,000 entries and either 64 binary bits or 32 ternary bits.

Using 64 of these tiles, the company designed a search processor that can hold 16 databases. The search engine chip, dubbed the IS51VV4064, can search four of these databases for addresses within the same clock cycle, which translates into 533 million table lookups per second.

ISSI said this is a more elegant approach than doing parallel searches using several CAM devices, each of which is capable of just one search per clock cycle.

"If you need parallelism and use separate chips it could lead to fragmentation problems," said Nelson Chow, director of engineering at ISSI.

Designers can choose to operate the device in either binary or ternary mode. In binary mode, the chip has a total capacity of 4Mb and supports search key sizes of up to 2Kb. When operating in ternary mode, the capacity drops to 2Mb and the maximum key size reaches 1Kb.

Other features of the search engine technology are the use of "aging" bits that clear out old and unused entries as well as static entry bits that hold certain entries in place.

The device, which is based on 0.13?m design rules, comes in a 480-ball BGA package and is available for sampling now. ISSI said it will also license the technology as an IP core to companies that want to embed smaller search engines into an ASIC.

Exact-match searches

Aside from designing smarter CAM engines, ISSI said it plans to soon license algorithmic search engines for exact-match tables used in Layer 4 flow tables as well as for the Ipv4 32-bit addressing standard. Unlike CAMs, which use a more specialized circuit design, these algorithms can be implemented in commodity SRAM or DRAM chips.

Chow said he expects these algorithms to be used for search engines that require large tables that hold more than 1 million entries. "These are tables where you would need to use 30 CAMs," he said.

Moreover, algorithms provide more deterministic delay, capacity and update times than search programs used today. The algorithms should be available by 2H of 2003, Chow said.

- Anthony Cataldo

EE Times





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