Computers: Kings, Queens and Silicon Chips

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It was a bad week for chess champions. As Anatoli Karpov was falling a game behind Gary Kasparov in the world chess championship at Moscow's Tchaikovsky Concert Hall, an upset of a different sort was taking place in Denver's Radisson Hotel. The world's top-ranked chess machine, a $14 million Cray X-MP/ 48 supercomputer running a program called Blitz, was about to lose the North American computer-chess championship to Hitech, a rack of custom-made silicon chips attached to a $20,000 Sun minicomputer.

While Karpov and Kasparov were face to face, the two computers were 750 miles apart--the Cray in Mendota Heights, Minn., the Sun on the Pittsburgh campus of Carnegie-Mellon University. The computers' moves were sent over telephone lines to Denver and relayed to a regulation chessboard. But distance did not hurt the game. Says Chess Master David Levy: "For the first time a program played like a strong human player."

Computers have been playing passable chess since 1966, when M.I.T. Student Richard Greenblatt wrote a program called MacHack that trounced Hubert Dreyfus, a Berkeley philosopher who had insisted that no computer would ever beat even a ten-year-old. Today chess machines defeat most casual players, and the best programs can hold their own against all but the top grand masters.

Chess-playing computers generally use a brute-force approach. Looking four to eight moves ahead, they examine every possible play and counterplay and choose the move that minimizes their opponent's gain. The Cray, scanning 100,000 chess moves per sec., can usually come up with a winner. Hitech lacks the Cray's huge memory and powerful processors, but it makes up for that with speed and clever play. Long-term strategy, for example, is controlled by a program named Oracle, which was created by Hans Berliner, an artificial- intelligence expert and former world correspondence-chess champion.

After choosing a line of attack, Oracle switches control to a separate unit called Searcher. Designed by Carl Ebeling, a Carnegie-Mellon graduate student, and manufactured under a Defense Department grant, Searcher is a bread-box- size device that contains 64 special-purpose microprocessors. Each is assigned & to one square of the chessboard. When a piece lands on a particular square, the microchip dedicated to that square determines the likely outcomes. Operating at peak speeds, the 64 chips can evaluate more than 175,000 positions per sec., or 30 million in the 3 min. allowed for each move of tournament play.

Two weeks ago in Pittsburgh, Hitech finished first in a ten-team tournament that included four chess masters. Last week it made short work of three weaker machines before taking on the Cray. Two hours into that game, a crack opened up in the Cray's king-side attack, and the minicomputer swooped in for the kill. Says Robert Hyatt, chief designer of the losing program: "We were at its mercy."