Encyclopedia of Computer Science and Technology

chip 85techniques. An ever-increasing search base could be combinedwith evaluation of particularly important positionalfeatures (such as the possibility of creating a “passed pawn”that could be promoted to a queen).By the end of the 1970s, International Master DavidLevy was still beating the best chess programs of the time(defeating Chess 4.7 in 1978). A decade later, however, Levywas defeated in 1989 by Deep Thought, a program thatran on a specially designed computer that could examinehundreds of millions of positions per move. That same yearWorld Champion Garry Kasparov decisively defeated themachine. In 1996, however, the successor program DeepBlue (sponsored by IBM) shocked the chess world by beatingKasparov in the first game of their match. Kasparovwent on to win the match, but the following year an updatedversion of Deep Blue defeated Kasparov 3 1/2–2 1/2. A computerhad arguably become the strongest chess player in theworld. As a practical matter, the match brought IBM invaluablepublicity as a world leader in supercomputing.Chess and AIThe earliest computer chess theorists such as Claude Shannonand Alan Turing saw the game as one potential wayto demonstrate true machine intelligence. Ironically, bythe time computers had truly mastered chess, the artificialintelligence (AI) community had concluded that masteringthe game was largely irrelevant to their goals. AI pioneersHerbert Simon and John McCarthy have referred to chessas “the Drosophila of AI.” By this they mean that, like theubiquitous fruit flies in genetics research, chess became aneasy way to measure computer prowess. But what was itmeasuring? The dominant brute-force approach was morea measure of computing power than the application of suchAI techniques as pattern recognition. (There is, however,still some interest in writing chess programs that “think”more like a human player.) In recent years there has beensome interest in programming computers to play the Asianboard game Go, where positional and structural elementsplay a greater role than in chess. However, even the latestgeneration of Go programs seem to be relying more on astatistical approach than a deep conceptual analysis.Further ReadingComputer History Museum. “Mastering the Game: A Historyof Computer Chess.” Available online. URL: http://www.computerhistory.org/chess/. Accessed April 28, 2007.Hsu, Feng-Hsiung. Behind Deep Blue: Building the Computer ThatDefeated the World Chess Champion. Princeton, N.J.: PrincetonUniversity Press, 2004.Levy, David, and Monty Newborn. How Computers Play Chess.New York: Computer Science Press, 1991.Shannon, Claude E. “Programming a Computer for PlayingChess.” Philosophical Magazine 41 (1950): 314. Available fromComputer History Museum. Available online. URL: http://archive.computerhistory.org. Accessed April 27, 2007.chipAs early as the 1930s, researchers had begun to investigatethe electrical properties of materials such as siliconand germanium. Such materials, dubbed “semiconductors,”were neither a good conductor of electricity (such as copper)nor a good insulator (such as rubber). In 1939, oneresearcher, William Shockley, wrote in his notebook “It hastoday occurred to me that an amplifier using semiconductorsrather than vacuum [tubes] is in principle possible.” Inother words, if the conductivity of a semiconductor couldbe made to vary in a controlled way, it could serve as anelectronic “valve” in the same way that a vacuum tube canbe used to amplify a current or to serve as an electronicswitch.The needs of the ensuing wartime years made it evidentthat a solid-state electronic device would bring manyadvantages over the vacuum tube: compactness, lowerpower usage, higher reliability. Increasingly complex electronicequipment, ranging from military fire control systemsto the first digital computers, further underscored theinadequacy of the vacuum tube.In 1947, William Shockley, along with John Bardeenand Walter Brattain, invented the transistor, a solid-stateelectronic device that could replace the vacuum tube formost low-power applications, including the binary switchingthat is at the heart of the electronic digital computer.But as the computer industry strove to pack more processingpower into a manageable volume, the transistor itselfbegan to appear bulky.Starting in 1958, two researchers, Jack Kilby of TexasInstruments and Robert Noyce of Fairchild Semiconductor,independently arrived at the next stage of electronicminiaturization: the integrated circuit (IC). The basic ideaof the IC is to make semiconductor resistors, capacitors,and diodes, combine them with transistors, and assemblethem into complete, compact solid-state circuits. Kilby didthis by embedding the components on a single piece of germaniumcalled a substrate. However, this method requiredthe painstaking and expensive hand-soldering of the tinygold wires connecting the components. Noyce soon cameup with a superior method: Using a lithographic process, hewas able to print the pattern of wires for the circuit onto aboard containing a silicon substrate. The components couldthen be easily connected to the circuit. Thus was born theubiquitous PCB (printed circuit board). This technologywould make the minicomputer (a machine that was roughlyrefrigerator-sized rather than room-sized) possible duringthe 1960s and 1970s. Besides the PCBs being quite reliablecompared to hand-soldered connections, a failed boardcould be easily “swapped out” for a replacement, simplifyingmaintenance.From IC to ChipThe next step to the truly integrated circuit was to form theindividual devices onto a single ceramic substrate (muchsmaller than the printed circuit board) and encapsulatethem in a protective polymer coating. The device then functionedas a single unit, with input and output leads to connectit to a larger circuit. However, the speed of this “hybridIC” is limited by the relatively large distance between components.The modern IC that we now call the “computerchip” is a monolithic IC. Here the devices, rather than being