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Intel unveils on Tuesday a technology designed to push notebook processor power beyond its current limits. This novel way to conserve and extend the CPU is called SpeedStep, and more than a dozen vendors are ready with notebooks that take advantage of it.

When your SpeedStep-equipped notebook is plugged in, the processor runs at top speed. When it's running on battery power, it "steps down" to a lower speed.

Here's the good news: After some delays, the technology has arrived--and it works. PC World tested three 650/500-MHz Pentium III notebooks, and they all ran plenty fast. Battery life on two of the units was outstanding. The surprising news: The notebooks managed almost identical battery life running at either speed, so we see little reason to run them at the slower speed.

Our Dell Inspiron 7500, Hewlett-Packard OmniBook 4150, and IBM ThinkPad 600X test models all came with Windows 98 and 128MB of memory. (Dell and HP sent us shipping units; IBM sent a preproduction model.) Prices range from $4199 for the HP to $4238 for the Dell and $4408 for the IBM. For a high-powered bargain, check out sibling 600/500-MHz systems: You won't take much of a performance hit, and you should save at least $200.

Meanwhile, for thin-and-light notebooks that can't handle the heat requirements of SpeedStep's higher frequency, Intel also introduces Tuesday new low-voltage parts. These PIII-500 chips run at 1.35 volts, which is the voltage used by PIII-400 mobile CPUs in today's thin-and-light machines. A family of 1.1-volt PIIIs for thin-and-light models will follow later in the year. Mainstream notebook users, however, can step up to 650 MHz now and enjoy the performance gain.

How SpeedStep Works

Intel's SpeedStep technology, also known by its code name "Geyserville," involves three components: the processor, a compliant BIOS that recognizes use of battery or AC power, and a motherboard chip that regulates voltage and speed. By focusing not only on the processor speed, but also on the voltage, Intel says it has reduced power consumption a great deal. And that's true: The new CPUs running at their top speed of 650 MHz consume 14.4 watts of power at 1.6 volts, numbers that plummet to 7.9 watts and 1.35 volts at 500 MHz.

But a processor is just one component. The screen, for example, gobbles up about 18 percent of the battery power most of the time, Intel estimates. When working at full capacity, the CPU is a significant drain on the battery, but usually the CPU doesn't work that hard. When you're performing office tasks like word processing or e-mail, notebook power management kicks in. Then, the processor runs at only a quarter to a third of its full power, according to Intel. Under these conditions, even a 40 percent drop in CPU power consumption makes little difference to overall notebook battery life. And that's exactly what our battery tests showed.