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IBM highlights Power chip power savings

Big Blue's dual-core PowerPC 970MP processor has a number of ways to reduce its power consumption when possible.

SAN JOSE, Calif.--IBM's new dual-core PowerPC 970MP processor employs several features to let the chip consume less power when possible.

The 2.5GHz chip is used in Apple Computer's latest Power Mac G5 Quad machines now and will be incorporated into IBM's blade servers in the first quarter of 2006.

Power consumption, whether in desktop, mobile or server computers, is a growing concern. Indeed, Intel highlighted performance per watt as the prime new feature of a next-generation chip architecture.

The PowerPC 970MP reduces its power consumption in a number of ways, Norman Rohrer, IBM distinguished engineer, said in a speech at the Fall Processor Forum here.

One major feature is that one core can shut down if it's not needed, Rohrer said. "You can cut the power roughly in half by shutting off one of the cores," he said.

The chip also can cut its frequency by half or a quarter. Peak power consumption of 100 watts drops to about 60 watts and 40 watts with those moves, he said.

In addition, the chip can run in a low-voltage mode that further cuts power. And in a "deep nap" mode, it can cut its frequency to one sixty-fourth of the regular speed. With both cores active but deeply napping, the processor consumes 5 watts; with one, it's 3 watts.

The dual-core PowerPC 970MP is something of a return to an earlier era for IBM. Its predecessors, the PowerPC 970 and 970FX, are single-core chips, but they're based on the IBM Power4, which became the first dual-core server processor when it made its 2001 debut.

Each core of the PowerPC 970MP has its own 1MB section of high-speed cache memory. Having separate caches allows the computer to shut down one cache along with the processor core if it's not needed, Rohrer said. The 1MB cache also gives a performance boost compared with the 512KB cache used in the PowerPC 970FX.