One of the items most mobile Mac users have on their wish list is a G5-powered PowerBook. Such a device, thus far, seems many months away, to say the least. The current crop of G5 processors, exclusively produced by IBM, require hefty heat management in the form of heat sinks and liquid cooling that canit be easily squeezed into the form factor of a laptop.
All is not lost, however, eWeek reports that IBM believes it has a way to get a G5 to run in a laptop and without it self-destructing, using a new technique called PowerTune. Whatis PowerTune? From eWeek:
IBMis design goal with PowerTune is to balance performance and power consumption. In addition, because the "leakage current" -- the amount of power that trickles away and is wasted -- is significantly higher at finer process technologies, such as used for the 970FX, IBM developed PowerTune.
The design approach somewhat differs from rival Intel Corp., which places as much emphasis on manufacturing as it does on design, if not more. While Intel has aggressively pushed new process technologies into the market, IBM has concentrated upon process improvements, such as silicon-on-insulator and doped silicon. Using materials with a low threshold voltage can improve the clock speed of a chip, but also increases the power lost to leakage current, IBMis Rohrer said.[...]
For example, PowerTune-savvy chip can be asked to drop down to a half or a quarter the rated frequency, or even down into a "deep nap" state where the chip can run at 1/64 of the rated frequency, Rohrer said.
Within each frequency iteration, the processor also can be instructed to run in idle or nap modes, which will reduce the operating voltage of the chip. The combination of voltage and frequency scaling, Rohrer said, will be PowerTuneis advantage, and is a much more flexible power-management scheme than its x86-compatible competitors.
Moreover, power modes can be entered and left relatively quickly, "on the order of several microseconds," Rohrer said. "Anytime you pause on the keyboard, after the time the system has to finish the last instruction, the system can enter deep nap."
This very informative, but lengthy article goes on to discuss PowerTune in more detail, and some of the other hurdles IBM and designers face in bringing the power of the G5 processor to a laptop. You can find the full article at eWeek News.