IBM to add clock throttling tech to 90nm G5 chip

PowerTune saves... er.. power

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.

In addition, the Power Mac G5 computer allows the user to control bus slewing mode. The options for specifying either high, reduced, or automatic processor and bus speeds are located at System Preferences>Energy Saver>Options; then select Automatic, Highest, or Reduced.

The IEEE ISSCC will also see the launch of the 90nm G5. IBM began sampling the part during the autumn, suggesting the part shouldn't be that far off shipment come launch time.

Indeed, AppleInsider yesterday claimed to have seen a detailed report covering Apple's next major Power Mac G5 update, due early next March. According to the story, the new machines will sport an updated North Bridge which adds 533MHz DDR 2 SDRAM and 1.5GHz FSB support - the latter is logical, given CEO Steve Jobs' promise to ship a 3GHz Power Mac next summer. ®