AT the World Checkers Championship here, the legendary Marion Tinsley sits quietly in his chair, pondering 30 or 40 moves ahead, occasionally chewing ice and drinking water.
His opponent, a supercomputer named Chinook, cannot think at all, but can chew through some 12 million possible plays a minute.
Dr. Tinsley, who has lost only nine games in the last 36 years, is squaring off against Chinook at the Boston Computer Museum for two weeks to help educate the public to the ``subtlety, beauty, and depth that lies within checkers,'' he says.
Tinsley is the absolute grand master of checkers - the acknowledged greatest checker player in the history of the game, stretching back to Socrates' time.
Tinsley would also like nothing better than to trounce a system that now has a staggering 8 billion bytes of disk memory. ``I'm not afraid of Chinook,'' says the lanky and soft-spoken man. ``I can go for a walk after this,'' he says, smiling, ``but Chinook can't.''
Chinook and Tinsley are squaring off for a 30-game match, usually four games a day. That his opponent is a computer, or more accurately, a software program run on a 16-processor system from Silicon Graphics in Mountain View, Calif., is the ultimate challenge for Tinsley, a retired mathematics professor from Conyers, Ga.
``In addition to the desire, energy, and memory that Tinsley has,'' says David Levy, a chess master from London, ``he has clarity of thought as well, the ability to sweep aside the dross. If he loses the match, it will not be because the computer has more understanding, it will be because Tinsley made a mistake.''
Which is possible, but highly unlikely.
``Tinsley is almost perfect,'' says Jonathon Schaeffer, a professor from the University of Alberta, Canada, and designer of the software program that is challenging Tinsley. ``I would like to think we could win, but after 50 years of this, Tinsley knows secrets and keeps them to be used at critical moments.''
Tinsley has faced Chinook before, beating the computer in the United States National Open in 1990 and in a major contest in 1992. But Chinook is more comprehensive and more powerful this time. ``We keep adding more and more to the database,'' says Mr. Schaeffer, ``including all the moves Tinsley has made in all his previous games.''
Just before the opening match, Tinsley is calm, chatting amiably in the small auditorium with fewer than 30 people watching. Checkers, always in the shadow of chess, needs Tinsley to bring wider appreciation to possibilities of the game.
His mastery of the complexity of checkers is even more remarkable when he confesses that his total commitment isn't what it used to be. ``In a way you could say I'm just doing this,'' he says, softly, ``because there was a time when I lived and breathed checkers; but not so much anymore.''
Behind him is a huge television monitor with a graphic display of a checker board with a disembodied hand that moves the checkers in response to the moves on the board in front of Tinsley. He sits down, and the match begins. Mr. Schaeffer is on the opposite side of the table, feeding information into the computer.
As a young boy, Tinsley stumbled across two books on checkers in a library in Irontown, Ohio. ``From then on I was hooked,'' he says. He became World Champion in 1954. Since then, no one has come close to beating Tinsley in 40 years. ``I applaud the computer,'' he says, ``but it's a little like a graduate student, fast and dedicated, but it can't think very well.''
Tinsley has a phenomenal memory. ``He can tell you moves he and his opponents made from 30 years ago,'' says Mr. Levy. ``What the computer has also is a huge amount of knowledge, but it lacks understanding.''
Tinsley doesn't dispute assessments of his abilities, but he says his capacity is derived from God. With humor, he says the ``program'' he follows is slightly superior. He doesn't believe God is telling him how to play, but says, ``I am using the abilities he has given me.'' He adds, ``I like to relax after a match by reading Psalms.''
On Monday, the first match between Chinook and Tinsley ended in a draw. Even though at first the computer refused to accept it, it reneged later when Tinsley convinced the ``machine'' it couldn't win.
The second game was more difficult for Tinsley. But by the fourth hour, the computer, with its capacity to know all possible moves when eight checkers remain on the board, knew another standoff was the result. Unbeaten, Tinsley shook hands with Schaeffer and stood up.
``Well, I made it today by the hair of my chinny-chin-chin,'' he says, ``Now I think I'll go for a walk.''