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Pentium Extreme Edition 955 vs. Athlon 64 FX-60


Deathmatch at $1K
— 2:32 AM on January 10, 2006

INTEL HAS JUST RECENTLY unleashed its latest desktop processor, the Pentium Extreme Edition 955, armed with a fistful of new technologies that sound mighty intimidating on a spec sheet. Intel manufactures this CPU using its brand-new 65nm process tech, and the Extreme Edition 955 sports dual processor cores with a higher clock speed, a larger cache, and faster bus than its predecessor. Not only that, but this new processor gets support from the also-new 975X chipset, Intel's first stab at core logic with a proper dual eight-lane PCI Express configuration for use with dual-graphics solutions like ATI's CrossFire. All told, the Extreme Edition 955 sounds like a formidable presence on paper, and it backs up that rep in person with better performance than any other desktop chip Intel has produced to date.

The Extreme Edition's stellar resume isn't likely to intimidate AMD, because Athlon 64 processors have been outperforming Intel's CPUs for a good while now. Just to be sure, though, AMD has cooked up its own new flagship CPU for release today, the Athlon 64 FX-60. The FX-60 isn't as flashy as Intel's new number, but it does represent a major change for AMD's high-end gaming-oriented processors, because it is the first dual-core member of the FX product line.

Now, these two new thousand-dollar processors face one another in our broad suite of performance tests, ranging from highly multithreaded 64-bit rendering applications to the latest games. Thanks to new multithreaded graphics drivers, these new dual-core CPUs may even challenge their single-core counterparts for supremacy in 3D gaming. Let's see whether the boffo specs on Intel's new 65nm Extreme Edition processor translate into a credible challenge for the dual-core FX-60.

Presler gets extreme
The Pentium Extreme Edition 955 is the top member of a whole new family of Pentium desktop processors from Intel. At the heart of this lineup is a single chip, code-named Cedar Mill, which is a rendition of the Pentium 4's familiar Netburst microarchitecture manufactured via Intel's 65nm fab process. Cedar Mill processors pack 188 million transistors into a die that's only 81 square millimeters—well below the 122mm2 of Pentium 4 "Prescott" processors thanks to the transition from 90nm to 65nm process tech. This reduction in die area comes in spite of the fact that Cedar Mill processors carry quite a few more transistors. Intel estimates Cedar Mill's transistor count at 188 million, versus 169 million for the version of Prescott that has 2MB of L2 cache. Cedar Mill also has 2MB of L2 cache, so the additional transistors likely come from other sources, including the addition of support for Intel's new virtualization technology, dubbed VT.

Cedar Mill chips support not only VT but the entire legacy of Intel alphabet-soup extensions, including MMX, SSE/2/3, EM64T, and HT or Hyper-Threading. This latest addition to the soup consists of a handful of new instructions intended to facilitate the creation and operation of multiple virtual machines on a single CPU, a la virtual machine software packages like VMWare. Hardware assisted virtualization can segment virtual machines at a lower level than software packages alone, allowing for better partitioning between VMs for the sake of security, stronger isolation of faults or crashes to a single VM, and higher performance. The use of virtual machines is largely confined to servers right now, but virtualization will likely spread to the desktop in the coming years for the sake of security or digital rights management schemes—or because I'd really like to run the MacOS alongside Windows, assuming Mr. Jobs will allow such crazy things to happen.

Intel will mix and match Cedar Mill silicon and features to the various products in its desktop CPU lineup, disabling Hyper-Threading or binning out clock speeds according to its needs. Cedar Mill chips in their most basic form will make up the Pentium 4 6x1 series of processors at clock speeds ranging from 3GHz for model 631 to 3.6GHz for the Pentium 4 661. These products will talk to the world via an 800MHz front-side bus and will not support VT technology.

The more radical implementations of Cedar Mill fall under the umbrella of the "Presler" code name. Presler is not a separate chip, but two Cedar Mill chips situated together on a single package to make a "dual-core" CPU. Like prior dual-core CPUs from Intel, Presler's two halves communicate with one another over a shared front-side bus, with no provisions for point-to-point intra-chip data transfers. Thus, there's really no performance penalty for moving to a two-chip design. There are manufacturing advantages, though. Any two Cedar Mill chips can be joined together to make a Presler processor, and the total surface area of the wafer that must be defect-free to produce a Cedar Mill chip is only the aforementioned 81 mm2. Yes, it has to happen twice, but not on adjacent portions of the wafer or even on the same wafer. Contrast that with with the die sizes of the Pentium D or the Athlon 64 X2—both roughly 200 square millimeters—and you begin to see the advantages of Presler's dual-chip-per-package approach. These puppies should be much cheaper to produce as Intel's yields ramp up on its 65nm process.

Presler CPUs will form the meat of Intel's desktop processor lineup, the Pentium D 900 series. The 900s initially range from the 920 at 2.8GHz to the 950 at 3.4GHz, all riding an 800MHz bus with 2MB of L2 per core. These products have VT support enabled but not Hyper-Threading. (Trust me, all of this somehow makes sense to the marketing majors inside Intel, if not the engineers.)

Our subject today, the Pentium Extreme Edition 955, is the fully-realized, self-actuated version of Presler with support cranked up for all of the goodies, including Hyper-Threading, VT, and 2MB of cache per core. The Extreme Edition also separates itself from the riff-raff with its ability to run on a 1066MHz front-side bus—a welcome development given the prevalence of dual-channel memory subsystems on Intel core-logic chipsets and the rise of DDR2 memory modules capable of running at 800MHz and beyond. Progress often comes at a penalty, and in this case, the price we pay is motherboard compatibility. Although the Extreme Edition 955 comes in the same LGA775 package as other recent desktop Pentiums, it requires additional voltage that can only be supplied by newer motherboards, such as the boards arriving alongside the Extreme Edition 955 that are based on the Intel 975X chipset.