The story sounds familiar: Intel hits a new milestone in nanometer architecture, and AMD waits a while to follow up. It happened with 65nm processors, and it's happening again now. Two days shy of a year since Intel launched Penryn, its first 45nm chip, AMD is finally ready to counter with a few 45nm CPUs of its own--Phenom II has finally arrived. But based on our hands-on testing of two Phenom II machines--the Dell XPS 625 and the Maingear Dash--the chip isn't quite as dominating as AMD would have you believe.

AMD Phenom II Explained

AMD is positioning Phenom II in between Intel's Core 2 Quad and Core i7 offerings. Phenom II chips are available in two versions, the X4 920 and the X4 940 Black Edition, which compete tit-for-tat against Intel's highest Core 2 Quad CPU frequencies at 2.8 and 3.0 GHz, respectively.

AMD bumped the shared L3 cache of the Phenom II processors up from 2MB to 6MB, giving each CPU a total cache of 8MB. L3 cache serves as a shared memory space for the cores to draw from. Increasing the amount improves the CPU's ability to pull data from this faster memory space instead of having to issue slower requests to the system's main memory. The move puts Phenom II processors right in the middle of Intel's Core 2 Quad lineup for cache size, but the result is still short of the 12MB caches found on higher-end Core i7 chips.

Though limited overclocking of the 920-edition processors is available through AMD's OverDrive software, the company is tipping its hat toward the extreme-performance crowd with its Black Edition processors. These CPUs run multiplier-unlocked, which liquid-nitrogen-armed enthusiasts have been able to exploit to frequencies above 6 GHz, surpassing the world record for Intel Core i7 processors, which stands at 5.5 GHz.

Performance

The Phenom II's integrated memory controller and HyperTransport interface give it a technical edge over competing Core 2 Quad chips, which lack those features. Intel moved to an integrated memory controller and began incorporating its own version of HyperTransport--dubbed QuickPath Interconnect--only with its Core i7 platform. The integrated memory controller and HyperTransport interface allow Phenom II processors to achieve a higher memory bandwidth than Core 2 Quad processors can, by eliminating the bottlenecks created by a frontside bus and an external controller. The arrangement, in theory, improves system performance.

But not in practice, apparently. In comprehensive PC World lab testing of two $1499 Phenom II-based desktops, Dell's XPS 625 and Maingear's Dash, these brand-new chips failed to blow Intel's Core 2 Quad and Core i7 offerings out of the water.

The Phenom II systems crushed most of our top-ranked sub-$1500 value PCs, but that's to be expected, as they have twice the cores and are generally almost twice the price of predominantly Core 2

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