This Wednesday, Intel will launch a new processor. That's not exactly a stop-the-presses development. What is novel, however, is that this processor doesn't emphasize everybody's favorite yardstick: clock speed.

The Pentium M, as the Santa Clara, Calif., chipmaker has christened the new processor, is the first Intel chip designed from the start for use in laptop computers, where efficiency is as crucial as raw speed.

The Pentium M -- also to be sold under the "Centrino" moniker when packaged with an associated set of system chips and a WiFi wireless receiver -- abides by a slacker's work ethic: It performs the minimum effort necessary at any time and sleeps on the job as often as possible.

It does this by throttling back its clock speed and voltage, then slowing or shutting off subsystems as they go out of use, even momentarily. For example, Intel says the Pentium M will dip into its low-power mode between rendering each frame of a DVD movie. It will also power off parts of its 1-megabyte memory cache as needed. And one Centrino video chipset can even command a laptop's screen to delay its refresh rate if it isn't displaying any fast-moving images.

The idea behind this is to make smaller, longer-running portable PCs not just possible -- ultra-light machines with low-voltage processors from Intel and competitor Transmeta have done this for years -- but powerful. (Apple laptops have delivered better battery results as well but haven't kept pace with the dramatic growth in clock speeds on Windows laptops.)

I've been testing one Pentium M-equipped laptop for the past two weeks, Dell's upcoming Inspiron 600m. This machine, with a 14.1-inch screen and DVD-ROM/CD-RW combo drive, looks and works much like any other general-purpose laptop, but for three traits that give away its 1.4 GHz Pentium M.

First, Windows XP's battery-life estimates were wildly unreliable, jumping up and down every few minutes by an hour or more. Dell says the battery-meter software needs to be revised to keep pace with the processor's frequent power-saving adjustments.

Second, the 600m's underside doesn't risk scorching your skin when it runs on battery power, and its fan rarely pushes much air or makes much noise.

Third, the pre-production 600m I tested delivered some remarkable run-time figures for a screen that size, one of the biggest consumers of electricity on a laptop. In a worst-case test -- playing a DVD with the screen at maximum brightness and the internal WiFi receiver left on -- the 600m's lithium-ion battery ran for 2 hours and 15 minutes. It lasted about three hours while playing a digital-music collection and stayed on for four hours with the screen at minimum brightness.

Dell says 600m versions with smaller displays will run for longer than the model I tested, and production hardware may offer additional improvements. (The version I tested omits a Centrino WiFi receiver in favor of Dell's own hardware; Intel says its wireless gear uses less power than competitors'.)

This processor had no problem with everyday computing tasks, crunching CDs into Windows Media Audio files as fast as any desktop system I've tried lately. Finally, at 51/2 pounds (a gaudy, plastic-wood cover for the lid adds half a pound and subtracts any semblance of style) and pricing from $1,300 to $1,400, this laptop -- and others like it -- shouldn't require unpleasant trade-offs between cost and weight. It makes a decent case for Intel's new hardware.

But home users may not care. Intel's Centrino and Pentium M efforts face two major marketing problems -- one of which is largely Intel's own fault.

The first is the decreasing importance of battery life to many laptop users. Over the past year, hefty but cheap laptops built around desktop-grade Pentium 4 processors have become one of the most popular segments of the laptop market.

What these laptops' buyers want are a low price, a big screen and a fast processor, not just freedom from an electrical outlet. A desktop machine can provide all that, but only at the cost of giving up one's desk to a bulky tower case, stand-alone monitor and speakers, and yards of cables.

The second issue is the Pentium M's advertised speeds. Available in 1.3, 1.4, 1.5 and 1.6 GHz versions, it will look significantly slower than existing Pentium 4 and Pentium 4-M processors.

Intel says that's not important, since the efficiency it has wrung out of the Pentium M lets it do more in each clock cycle. "We will actually surpass the performance of the fastest mobile Pentium 4," said Don MacDonald, the company's marketing director for mobile products. He cited benchmark tests done in February that showed a 2.4 GHz Pentium 4-M being beaten to the finish line by a 1.6 GHz Pentium M.

Other manufacturers have made this claim before. Intel's chief rival, Advanced Micro Devices, no longer even advertises its Athlon processors' clock speeds, instead labeling them by their performance relative to other processors. Apple routinely makes this argument as well.

But Intel has relied on megahertz marketing for years, to the point where the market lacks any other standard vocabulary to describe a computer's speed. Now Intel will run into the same problem AMD and Apple have had for years: You can't go into a store and see a figure that counts everybody's clock cycles equally. If the Pentium M gets Intel to start speaking this kind of language, that alone will be a newsworthy development.

Living with technology, or trying to? E-mail Rob Pegoraro at rob@twp.com.