The first match began on 10 February 1996, in which Deep Blue became the first machine to win a chess game against a reigning world champion (Garry Kasparov) under regular time controls. However, Kasparov won three and drew two of the following five games, beating Deep Blue by a score of 4–2 (wins count as 1 point, draws count as a ½ point). The match concluded on 17 February 1996. After the match, Deep Blue was upgraded (unofficially nicknamed "Deeper Blue") and played Kasparov again in May 1997, winning the six-game rematch 3½–2½, ending on 11 May. Deep Blue won the deciding game after Kasparov made a mistake in the opening and became the first computer system to defeat a reigning world champion in a match under standard chess tournament time controls. The Deep Blue chess computer that defeated Kasparov in 1997 would typically search to a depth of between six and eight moves to twenty or even more moves in some situations. David Levy and Monty Newborn estimate that one additional ply (half-move) increases the playing strength between 50 and 70 Elo points. Writer Nate Silver suggests that a bug in Deep Blue's software led to a seemingly random move (the 44th in the first game of the second match) which Kasparov misattributed to "superior intelligence". Subsequently, Kasparov experienced a decline in performance due to anxiety in the following game, though he rejects this interpretation. After the loss, Kasparov said that he sometimes saw deep intelligence and creativity in the machine's moves, suggesting that during the second game, human chess players had intervened on behalf of the machine, which would be a violation of the rules. IBM denied that it cheated, saying the only human intervention occurred between games.  and demanded a rematch, who refused and dismantled Deep Blue. The rules allowed the developers to modify the program between games, an opportunity they said they used to shore up weaknesses in the computer's play that were revealed during the course of the match. Kasparov requested printouts of the machine's log files, but IBM refused, although the company later published the logs on the Internet. Computer scientists believed that playing chess was a good measurement for the effectiveness of artificial intelligence, and by beating a world champion chess player, IBM showed that they had made significant progress. Kasparov called Deep Blue an "alien opponent" but later stated that "It was as intelligent as your alarm clock". According to Martin Amis, two grandmasters who played Deep Blue agreed with each other that "It's like a wall coming at you".