Commentary for black move 21:

MAURICE ASHLEY: Deep Blue has responded dxe 5, so it is temporarily up a off and on. -- pawn. For those of you who are not aware of it -- 21...Qf4.

MAURICE ASHLEY: For those of you who are chess fans, you know what a pawn is worth. It gets to the other side, it could become a girl, and then you're really in trouble. And so a pawn is nothing to sneeze at. And we have here a pawn sacrifice by Kasparov, what we call compensation. Before we get into the explanation. /KPWEPBGS, of what /KPWEPBGS is, let's take a question. -- of what compensation is, let's take a question.

AUDIENCE MEMBER: Do you think that Deep Blue is a big step in chess technology, and why?

MAURICE ASHLEY: That Deep Blue is a big step in chess technology.

MIKE VALVO: Yes. It's a big step, it's advancing the parallel processor side of playing chess. The -- up to now the foremost computers have been mostly singly processor computers, this is a multiprocessor computer in a sense. It's got multiple chips that are playing chess, and the problem is coordinating them together. You've got five or six guys all have ideas what to do, how do you decide which one to choose?

MAURICE ASHLEY: This idea could easily backfire against a computer of Deep Blue's stature. He's sacrificed a pawn, the computer has looked deeply into the position -- Garry is a very efficient thinker, very deep clarity, but sometimes he makes a mistake in his calculation, we've seen it before, he makes blunders, he makes errors, he's only human, and as great a calculator as he is, almost like a mathematician in his ability to calculate so accurate and will so well, he does make mistakes, and if he has made a mistake now. The game is going to be over. That e-pawn is passed, it's in the center, it's restricting his pieces.

MIKE VALVO: Let's talk about the pluses here for black (Audience laughter.)

MAURICE ASHLEY: We do know the pluses. The knight plans to go to e6-c5-e4. Once this happens all of black's pieces are perfectly positioned, the e-pawn is dead, there's a centralized knight, white's pieces are back, white's pawns may prove to be weak in being this advanced. It's a clear plan that Garry has concocted.

MIKE VALVO: Plus he can make a lot of moves fast.

MAURICE ASHLEY: Right. He knows his plan so that gives him three or four moves for free that he can make very quick.

MIKE VALVO: And we can expect the computer to do strange things to try to hold onto that material.

MAURICE ASHLEY: That's correct, computers are so materialistic that they try to keep the pawn. It would be a shock for the computer to give the pawn back for positional compensation, that would be a little too human.

MIKE VALVO: Then Garry would really get upset. (Audience laughter.)

MAURICE ASHLEY: Another question from the audience.

AUDIENCE MEMBER: Mr. Hoane said computers will never play per chess but there are situations where they've already played per chess, for example when there are only five pieces on the board. And in these endgame databases, there's some very weird stuff, forced wins that are 70, 80, 100, 200-move forced wins, that to a human player, even a player who knows about endgames don't make much sense. I wonder whether you think that this might be -- what the future of computer chess is going to look like in 20 years' time at search depths have gone a lot further. Maybe computers will be playing the kind of chess that just looks alien to us, right? Beating us but in a way that just doesn't make sense.

MAURICE ASHLEY: Mike, I'll let you answer that question while I get fixed up here.

Real-time text commentary is made possible by LiveNote, Inc. and Vincent Varallo Associates