CPU, heal thyself

In the old days, computer vendors would often pull a fast one. They would tell you their system had the latest microprocessor when it actually had a cheaper, slower version running faster than the chip's rating permitted. So the shiny, new 500-megahertz system you thought you were buying might contain only an overclocked 300-MHz CPU. But the computer worked fine; indeed, it might have operated perfectly for years, with you none the wiser. And you perhaps replaced it only because a good buy on a 1-gigahertz machine eventually came along. How did that poor 300-MHz processor cope with such abuse? The short answer is that the manufacturer had set the clock speed low to ensure that its products would function without fault despite the inevitable variations among chips and among their different operating environments. Shady overclockers took advantage of that conservatism, inviting unpredictable failures when they eliminated the chipmaker's prudent safety margins. Lately, overclocking has gone mainstream. You can, for example, find competitions on the Web in which hardware hackers vie for top honors in this domain. Even chip manufacturers themselves are doing it in public trials to show off how blazingly fast their processors can run under the right conditions-like when they are being cooled with liquid helium to within a few kelvins of absolute zero.