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Fast Forward by Rob Pegoraro
A Processor's Clock Speed Is Just One Measure of Performance


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By Rob Pegoraro
Sunday, June 13, 2004; Page F07

The question I hear over and over from readers and friends goes something like this: "I need a computer for running Microsoft Office and browsing the Web, not much else. How fast of a processor should I get?"

It's not hard to see where that query comes from. Decades of computing history have taught one lesson very well: The most important part of the computer is the processor, and the higher the processor's clock speed, the better.

But this lesson plan badly needs a rewrite. First, ever-accelerating chip speeds have blown past the needs of many applications -- even the slowest machine sold today can handle most everyday computing tasks without perceptible delay. And for those chores where chip performance does matter, clock speed isn't the right measurement anymore.

While few people in the hardware business seem eager to say that processors are becoming a commodity, they are thinking anew about how to describe processing power. Over the past few years, AMD and Apple (whose chips had fallen behind Intel's in the clock-speed contest) have been vigorously advancing the "clock speed is obsolete" argument. AMD, Intel's chief rival, even went to the trouble of labeling all its processors with speed ratings that indicate which Intel chips they match up with best.

Now Intel -- the foremost exponent of megahertz and gigahertz as the prime numbers of personal computing -- is making its own move away from clock speeds to a new, three-digit numbering scheme.

So far, Intel has shipped seven processors under this system: the Pentium M 735, 745 and 755; the Mobile Pentium M 518, 532 and 538; and the Celeron M 340.

From eyeballing those numbers, picking a processor would seem quite simple: The Celeron is obviously the slowest, while the 755 Pentium M runs more than twice as fast.

Wrong. These numbers don't describe performance in any way.

Intel says they're supposed to reflect five processor features -- architecture (in terms of a chip's "die size," its dimensions when first cut from a wafer of silicon, with smaller sizes offering more efficient operation), Level 2 cache (a buffer of high-speed memory to store frequently used snippets of code), clock speed, front-side bus (which sends data between the processor and the rest of the system), and a generic category of "future Intel technologies."

But no formula determined that the Pentium M 755 would bear that number and not 734 or 737. As Intel says on its Web site (, "the digits themselves have no inherent meaning."

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