We’re going to be hearing a lot about neural networks and associative memory chips over the next few months and years, for they are likely to be the building blocks for computer systems that are already beginning to exhibit an almost chilling degree of machine intelligence. At the International Solid State Circuits Conference last month, AT&T Co described a neural network associative memory chip in CMOS that implements an algorithm based on a biological neural network that can recall 10 vectors within the memory in 500nS. The chip includes 54 amplifiers and 6K-bits of static RAM, and programmable interconnections, and integrates 75,000 transistors in 2.5 micron CMOS. But the Japanese are galloping down the same road, and Microbytes Daily reports that NEC has prototyped an Intelligent String Search Processor – an application-specific neural network chip. The NEC part is designed to search text for a specific character string, including vague strings – fuzzy matching. It compares text one character at a time against a pre-stored character string, at a claimed speed of 10m characters a second. Up to 64 character strings can be stored, with each string a maximum of 8 characters long. Each character is expressed with 16 bits to enable the system to support Kanji searches and input text is compared with the 64 stored strings in parallel. It tolerates poor spelling by signalling a near match when it sees one. The NEC chip is made up of associative memory and what the company calls a non-deterministic finite automaton structure. The target character string is stored in associative memory, and then a single character of the text to be searched is compared simultaneously with all target strings in memory. If there is a character matching the input character in the associative memory, a match signal is generated internally and sent to the Finite Automaton structure, which compares the stored characters and the input characters sequentially. When the entire string matches, a complete match signal is output. Other operational modes such as don’t care – acceptance of extra characters in the character string, and anchor – separation of words with delimiters such as commas and spaces, are supported. NEC will enhance the chip by increasing the size of the associative memory and adding on-chip macro commands, and looks to have something on the market in about two years.
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