Self adjusting chips

A TEAM of scientists at the University of Rochester is undertaking the next step in computing-designing a chip that reconfigures itself as it runs, adapting to the needs of software while processing faster and using less power while doing so. The adaptable chip signals an effort to take full advantage of the massive processing power that chip makers now deliver to desktops every day.

David Albonesi, assistant professor of electrical and computer engineering at the University of Rochester, leads the team, which has created a model called Complexity-Adaptive Processing (CAP) that monitors the way a piece of software uses the microprocessor hardware, and then adapts that hardware accordingly. The result is a more efficient processor that doesn't dawdle while running many tasks. Early tests have shown CAP to be able to halve the energy consumption of part of the chip while also improving performance.

The innovation came to Albonesi one Saturday when he decided to lock himself in a room and not come out until he'd thought up something novel. He started to look into certain inefficient parts of a chip, such as the cache, a kind of storage closet on the chip where frequently needed information can be stowed and accessed quickly. Most microprocessors today contain two types of cache, with a larger, slower cache acting as a backup to a smaller, faster one. Although the sizes of these caches are fixed in today's microprocessors, different programs require different sizes to run most efficiently. The team has a number of other tricks that it expects will produce even greater improvements, including changing the value of "one." Microchips send information by means of "zeros" and "ones," with the zeros represented by no voltage, and the ones represented by a voltage high enough to be detected above the background noise of electricity flowing through the chip. By reducing such things as the cache size, the scientists can lower the overall noise in a particular part of a chip, allowing them to lower the voltage needed to represent a one and thus saving energy. Like the changing cache size, this alteration can be done and undone as needed, millions of times each second, as the processor cranks along.

The CAP model may be able to save even more energy by offering ways to switch fewer transistors in the chip between one and zero, and by slowing down the processor's speed and lowering the voltage when it detects that a program can get by on less.

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Section  : Science & Tech
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