Centrino: It's Not Just the Pentium M: Page 2

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Centrino: It's Not Just the Pentium M

As for Intel, the chip giant is risking some confusion in that not all notebooks with the new Pentium M processor will bear the Centrino Mobile Technology brand. The latter honor is reserved for 100-percent "Intel inside" portables, so to speak, built around not only the Pentium M but one of Intel's two new 855 chipsets and its Pro/Wireless 2100 network adapter (codeveloped by Intel and Cisco Systems).

The new chipsets are the 855PM, which supports separate (third-party) AGP 4X graphics controllers, and 855GM, which integrates the latest version of Intel's Extreme Graphics (dubbed Extreme Graphics 2) for budget notebooks. Both combine Intel's latest battery-thrifty tricks, such as an internal timer that automatically turns off the chipset clock when the chipset is inactive, with support for up to 2GB of DDR266 memory; they share a Southbridge controller hub with two ATA/100 channels, AC97 audio, modem, 33MHz PCI/CardBus, and USB 2.0 support (Bluetooth wireless connectivity options will piggyback on the latter).

AMD has already issued a dig at Intel's house-brand 802.11b solution, noting that Athlon XP-M processors "are designed with an open architecture, helping to ensure that the best available 802.11 wireless solutions from leading companies can be easily integrated" into AMD-based systems. Lots of laptops already offer the faster if 802.11b-incompatible 802.11a or dual-band wireless network support that Centrino, at least for now, lacks, and many more are sure to adopt the high-speed yet backwards-compatible 802.11b successor 802.11g when silicon based on that new standard appears this fall.

Intel retorts that it'll add 802.11a and other wireless protocols to the Centrino platform soon, and that its current WiFi implementation is smartly optimized to do everything from coexisting with and automatically choosing between 802.11b and Bluetooth (if both are present) to seamlessly managing unplug-and-play, no-reboot-or-interruption transitions between wired to wireless office networks (or all the 802.11b hotspots in Borders, McDonald's, and other places it's helping to add to the WiFi roster of Starbucks and hotels).

Intel's Best Engineering (But No Hyper-Threading)

Meanwhile, AMD's PR-rating marketeers will be more than issuing a dig at the new Pentium M; they'll be singing "I told you so" in 20 languages as Intel joins AMD in declaring that instructions per clock cycle, not just raw clock-speed increases requiring big batteries and noisy cooling fans, are the key to PC performance. The fastest Pentium M runs at 1.6GHz, but Intel says its tests with BAPCo's MobileMark 2002 benchmark show it delivers 15 percent quicker performance than the 2.4GHz mobile Pentium 4 -- while getting up to five hours of battery life to a comparable mobile P4 system's three.

What's the secret to the new 0.13-micron-process CPU's performance? Well, for one thing, while it has the same 400MHz front-side bus speed as what we used to call the Pentium 4-M, the Pentium M has more on-chip cache -- 64K of Level 1 (32K instruction, 32K write-back data) and a whopping 1MB of Level 2 cache.

Deeper, darker Pentium M science includes advanced branch prediction -- not only capturing standard program behaviors but enhancing support for newer programming paradigms such as just-in-time and object-oriented code, and according to Intel reducing branch mis- (or miss-) predictions by more than 20 percent -- and a hardware-based (rather than more power-hungry, micro-operations-based), dedicated stack manager that reduces the overall number of micro-ops required.

More exotic yet, micro-op fusion combines two micro-operations into one, treating certain pairs of x86 instruction segments as a single segment through most of their trip through the CPU pipeline and then resplitting them just in time for execution. The Pentium M supports the SSE2 multimedia extensions to the instruction set first seen in the Pentium 4, but lacks the Hyper-Threading technology that optimizes the 3.06GHz desktop processor for multithreaded applications and multitasking environments.


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