Web Extra: AMD PowerNow

Although some people complain that the major issue behind batteries is the lack of running time, not everyone thinks it's a big deal. "Of course users would be willing to use a system that runs longer," says Martin Booth, product marketing manager, computation products group for AMD (Advanced Micro Devices). "But realistically, system usage is often near an AC power source--at one's desk, home, hotel or even on many flights these days--so for a large number of users, this is not a huge issue."

As CPUs get faster, power management based on application demand becomes desirable and is a key factor in extending battery life. AMD's PowerNow! technology lets the system automatically adjust CPU performance based on application usage, making it easy for people to use. A notebook's system battery life can be extended up to 30 percent with this type of technique.

A person sitting on a plane and only going through e-mail or writing a Word document doesn't need a notebook system's maximum power capability, so why not save it? Booth compares a notebook's increased capability via a processor with AMD's PowerNow! technology to the increase that Li-ion has brought to batteries. He says that although the maximum thermal power is increasing, innovations such as AMD's PowerNow! technology are helping reduce average power consumption.

AMD's PowerNow! technology is available in its seventh-generation Mobile AMD Athlon processor, targeted at performance and commercial notebooks (typically starting at more than $1,800), and its Mobile AMD Duron processor, targeted for the value segment of the notebook PC market.

AMD PowerNow! technology is a combination of hardware and software designed to extend battery life and deliver dynamic performance on demand. The technology runs notebooks on one of three selected operating modes: automatic, high performance or battery saver. In automatic, mode, the system will continuously vary the processor frequency and voltage between multiple (four or more) different performance states depending on what is required by currently running applications. This selection ensures that enough power is used to present each application at its best possible performance level while extending battery life when possible.

The maximum performance state is consistently maintained if the high performance operating mode is selected, and the battery saver mode runs the system at the lowest power state regardless of function, thus optimizing battery power but decreasing performance. Keep in mind that if you're only working on a text document, it may not matter at all that performance is down; if you're watching a DVD, however, that's another story.

Tests were conducted on the Mobile AMD K6-2+ processor on equivalent systems to show the different operating modes' effects on battery life. In performance mode, the system battery functioned for 3:06; an additional 1:11 of running time was gained using the battery saver mode, a 38 percent improvement. Similarly, a DVD of "Lost in Space" was played, which has a run time of 2:10. In performance mode, the battery ran out with a half-hour of the movie remaining, whereas in automatic mode, the movie ended and the battery had 11 percent of its capacity left.

Booth is well aware of the popularity and consumer familiarity of Intel's Pentium III processor with Speedstep technology. When asked to differentiate PowerNow! from the Intel Speedstep, he says that Intel's product is geared for increasing desktop performance whereas PowerNow! focuses on maximizing battery life (but at the expense of performance only if so chosen by the user). Also, Speedstep runs in "a fixed state; it's not dynamically adjustable like PowerNow! It can't manage performance levels on the way down to the lowest state--it only has a high and a low, nothing in between." AMD PowerNow! technology has up to 32 different operating levels, he says, providing more flexibility for OEMs and end users. Speedstep also does not run in an automatic mode and is only available in Intel's high-end processors, not the Celeron, whereas AMD PowerNow! technology can be found at all price points.

A number of manufacturers have shipped notebook PCs with AMD PowerNow! technology, including Hewlitt-Packard and Compaq. But many users probably aren't aware of it or bother to read the manuals to find out how to use it, which is ok because it automatically runs in the background. "However, if a user cares to, he can [further] adjust the settings on his machine," says Booth.

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