Intel faces some marketing challenges in getting consumers jazzed up about performance per watt.

FORBES: Chief Executive Paul Otellini

Intel Chief Executive PaulOtelliniPaul Otellini says megahertz and gigahertz is out, and "performance per watt" is in.

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The performance per watt is supposedly 3x that of the G5, and Apple is stuffing a pair of the chips in each new Mac Pro.

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Performance per watt is a way of measuring not just how fast a computer can grind data, but also how much power it uses when doing so.

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It delivers up to three times more performance per watt than the Fermi streaming multiprocessor, making it possible to build a supercomputer that delivers one petaflop of computing performance in just 10 server racks.

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Even though the Graphics Core Next GPUs have been slightly underclocked to 825MHz, and even though they technically offer better performance per watt than a single-GPU configuration, their overall 375w power draw could still get you in trouble with your local power station.

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Where they once boasted about performance, computer-makers now talk about performance-per-watt, and emphasise their energy-saving credentials.

ECONOMIST: Computers and the environment

These new processors will take advantage of new energy-saving features in Haswell and provide balanced performance-per-watt, giving customers even more options.

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Mark Van Den Berg, managing director at VantagePoint, says Bridgelux has been able to reduce costs ten-fold and improve performance (on a lumens per watt basis) at least three-fold since 2006.

FORBES: Magazine Article