IBM to add clock throttling tech to 90nm G5 chip

IBM is adding Intel SpeedStep-style clock frequency and core voltage scaling technology to the 90nm version of its PowerPC 970 processor, aka the G5. IBM engineers will be discussing the technology, dubbed PowerTune, next February at the IEEE Solid-State Circuits Conference, scheduled to be held in San Francisco. According to the pre-conference programme, IBM will unveil PowerTune during an 18 February conference session. PowerTune is described as "a power-management technique for a multi-gigahertz superscalar [64-bit] PowerPC processor in a 90nm technology [offering] a dynamically controlled clock frequency with noise suppression as well as a synchronisation circuit for a multi-processor system".

It's the latter point that separates PowerTune from SpeedStep-style technologies, allowing two or more processors to ensure they're running at the same clock speed, even though they may be loaded differently according to the way the host operating system is balancing tasks across the available CPUs. IBM undoubtedly has its eye on multi-processor blades, but the technology will also help Apple speed the arrival of G5-based PowerBooks, helped by the shift to a 90nm process.

The 130nm G5-based Power Mac already offers a level of frequency switching, throttling clock speed down to 1.3GHz, and the bus speed to 650MHz, but this appears to be a system feature, rather than a technology implemented in the processor.

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