A ashto n mo re lif e f o r mo o res law businessweek

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Unformatted text preview: s lo catio n in The Dalles, Orego n, is charged a co st per kilo watt ho ur o f two cents by the lo cal po wer pro vider, less than o nef if th o f the eleven-cent rate the f irm pays in Silico n Valley.S. Mehta, “Beho ld the Server Farm,” Fo rtune, August 1, 2006. Also see Chapter 10 "So f tware in Flux: P artly Clo udy and So metimes Free" in this bo o k. This dif f erence means big savings f o r a f irm that runs mo re than a millio n servers. And while these po werf ul shrinking chips are getting ho tter and mo re co stly to co o l, it’s also impo rtant to realize that chips can’t get smaller f o rever. At so me po int Mo o re’s Law will run into the unyielding laws o f nature. While we’re no t certain where these limits are, chip pathways certainly can’t be sho rter than a single mo lecule, and the actual physical limit is likely larger than that. Get to o small and a pheno meno n kno wn as quantum tunneling kicks in, and electro ns start to slide o f f their paths. Yikes! Buying Time One way to o verco me this pro blem is with mult icore microprocessors, made by putting two o r mo re lo wer po wer pro cesso r co res (think o f a co re as the calculating part o f a micro pro cesso r) o n a single chip. P hilip Emma, IBM’s Manager o f Systems Techno lo gy and Micro architecture, o f f ers an analo gy. Think o f the traditio nal f ast, ho t, single-co re pro cesso rs as a three hundred-po und lineman, and a dual-co re pro cesso r as two 160-po und guys. Says Emma, “A 300-po und lineman can generate a lo t o f po wer, but two 160-po und guys can do the same wo rk with less o verall ef f o rt.”A. Ashto n, “Mo re Lif e f o r Mo o re’s Law,” BusinessWeek, June 20, 2005. Fo r many applicatio ns, the multico re chips will o utperf o rm a single speedy chip, while running co o ler and drawing less po wer. Multico re pro cesso rs are no w mainstream. To day, mo st smartpho nes, P Cs, and lapto ps so ld have at least a two -co re (dual-co re) pro cesso r. The Micro so f t Xbo x 360 has three co res. The P layStatio n 3 includes the so -called cell pro cesso r develo ped by So ny, IBM, and To shiba that runs nine co res. Intel has even demo nstrated chips with upwards o f f if ty co res. Multico re pro cesso rs can run o lder so f tware written f o r single-brain chips. But they usually do this by using o nly o ne co re at a time. To reuse the metapho r abo ve, this is like having o ne o f o ur 160po und wo rkers lif t away, while the o ther o ne stands aro und watching. Multico re o perating systems can help achieve so me perf o rmance gains. Versio ns o f Windo ws o r the Mac OS that are aware o f multico re pro cesso rs can assign o ne pro gram to run o n o ne co re, while a seco nd applicatio n is assigned to the next co re. But in o rder to take f ull advantage o f multico re chips, applicatio ns need to be rewritten to split up tasks so that smaller po rtio ns o f a pro blem are executed simultaneo usly inside each co re. Writing co de f o r this “divide and co nquer” appro ach is no t trivial. In f act, develo ping so f tware f o r multico re syste...
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