Benchmark buffs called its performance underwhelming when it debuted in late 2000, but today -- running at double that original version's front-side bus and more than double its clock speed, with quadruple its Level 2 cache -- no one can deny that Intel Corp.'s Pentium 4 is a fast, powerful processor.

But the handwriting is nonetheless on the wall, or in Intel's marketing materials: As the chip giant this week introduces a new model-numbering scheme to replace simple core-speed metrics, the place of honor goes not to the Pentium 4 but to Intel's slimline-laptop CPU, the Pentium M, with three new Pentium M chips that show off the company's cutting-edge silicon technology.

And looking ahead, Intel has confirmed that evolutions of the efficient Pentium M design, not the Pentium 4's NetBurst architecture, will anchor its desktop and server as well as laptop lines as the company moves toward dual-core processor offerings in 2005 -- the Pentium 4 successor codenamed "Tejas" has been scrapped. (The P4 should, however, last long enough to move from today's 90-nanometer to 65-nanometer process technology and perhaps a dual-core model.)

Meet the New Boss

This week's new processors are the Pentium M models 735 (1.7GHz), 745 (1.8GHz), and 755 (2.0GHz), priced at $294, $423, and $637 respectively in 1,000-unit OEM quantities. Formerly known by the codename "Dothan," they mark the Pentium M's move from 0.13-micron to 90-nanometer process manufacturing -- just as February's 90-nanometer "Prescott" or "E" version of the Pentium 4 succeeded the 0.13-micron "Northwood" or "C" variant.

But the Pentium M makes the transition more successfully: While Prescott's relatively high heat and power consumption have been the buzz of the desktop market, Dothan draws even less power than the original Pentium M (21 versus 24.5 watts), despite packing almost twice as many transistors (140 million versus 77 million). It also fits into the same sockets, making the transition easy for laptop manufacturers.

Many of those new transistors are added cache: The Pentium M's Level 1 caches -- 32K apiece for instructions and data -- are unchanged, as is its 400MHz front-side bus speed (533MHz versions are expected later this year). But the Level 2 cache has doubled from 1MB to 2MB. Between the extra cache, smaller transistors, and strained-silicon process technology that "stretches" the silicon lattice to permit faster flow of electrons, Intel says the Pentium M 735 delivers approximately 10 percent higher performance than the previous top of the line, the same-clock-speed Pentium M/1.7; the 745 and 755 are naturally faster still.

Intel has also tweaked the Pentium M's microarchitecture, with an enhanced register access manager that handles CPU registers more efficiently for situations like a partial-length write followed by a full-length read, and a data prefetcher that enables more efficient speculation and loading into L2 cache of data likely to be requested by the CPU.

Dothan also represents the latest and greatest version of Intel's SpeedStep technology that balances power consumption and application performance to maximize notebook battery life. While the Mobile Pentium 4 can switch between only two frequency and voltage settings, the new processor supports multiple steps -- the Pentium M 755 can throttle from 2.0GHz all the way down to 600MHz, or 1.8GHz, 1.6GHz, 1.4GHz, 1.2GHz, 1.0GHz, or 800MHz in between.

About Those Processor Numbers

Since moving to its officially-Athlon-but-everyone-assumes-Pentium-4-equivalent performance ratings, such as the Athlon XP 3000+ and Athlon 64 3400+, AMD has made shoppers hunt through online technical documents to find the actual clock speeds of its CPUs. Intel, by contrast, isn't shy about revealing the new Pentium M processors' speeds (a company press release says the chipmaker intends "that feature specifications for all processors will be made public and easily accessible to help end customers compare processor features ... and make educated purchase decisions."

But it also says it's time to look beyond mere megahertz, and to help consumers "analyze or take into account more than one processor feature during the selection process." In other words, time for relative model numbers, which make their debut with the Pentium M this week and will appear on new desktop CPUs in June.

Hence, the full name of the new 2.0GHz Pentium M is "Intel Pentium M processor 755." And while this week's three newcomers differ only in clock speed, Intel emphasizes that that's only one of five factors that will go into placing future chips on the numeric spectrum: Architecture, including smaller process technology or other enhancements; the amount of on-chip cache; front-side bus speed; and other Intel-developed technologies, such as Hyper-Threading (still absent from the Pentium M line), will play a part.

Intel also insists that three-digit numbers beginning in 7, as assigned to the Pentium M and its Low-Voltage and Ultra-Low-Voltage variants, are not "better" than numbers beginning in 5 -- for mobile and desktop Pentium 4s -- or those beginning in 3 -- for mobile and desktop Celerons. Shoppers are supposed to first pick a processor family based on their budget and intended uses for a computer, then use the processor numbers to compare chips within that family, not to compare numbers across families.