Review: Subpar performance from AMD's Phenom quad-core CPU

(CNET.com) -- For raw performance, AMD's Athlon 64 X2 chips have lingered behind their Intel Core 2 Duo counterparts all year. Only aggressive pricing from AMD kept its old dual-core CPUs in systems and on store shelves.

According to our testing, AMD will have to work similar magic with its new quad-core Phenom chips. If you want a quad-core PC now, and you can find a prebuilt PC that uses a Phenom 9600 for significantly less than a similar desktop with an Intel Core 2 Quad Q6600, go for it. But unless you can find it for an exceptional price, we advise against the Phenom right now, because its performance simply isn't there.

AMD has made much of the fact that its Phenom is the first "true" quad-core CPU. Technically this is correct. While Intel's Core 2 Quad design basically melds two dual-core chips together, AMD's Phenom is the first to include four cores that all share at least one level of cache, in this case, the Level 3 cache. Similar to recent advances in 3D chip design, the Phenom's unified L3 cache provides a data store whose size changes depending on the amount of data coming through.

Its flexibility ranges from pumping out one large chunk of data to a single core, or sending four smaller chunks across all four processors. In theory, that dynamic distribution of work should give Phenom an advantage over Intel's Core 2 design. The problem is that neither the size of the data chunks nor the speed at which Phenom can process them, give AMD's new chips enough of a boost.

Over the next few months, AMD will expand its Phenom offerings to include two higher-end models, the Phenom 9700 at 2.4GHz, and the 9900 at 2.6GHz. We also expect that Intel will add to its Core 2 family by bringing its new, more heat- and power-efficient 45 nanometer design into mainstream dual-core and quad-core CPUs.

Our test of the first of these new parts, the Core 2 Extreme QX9650, showed that Intel's new design makes a noticeable performance impact over Intel's older 65 nanometer parts. That doesn't bode well for AMD and the 65-nanometer Phenom, which can't overtake even Intel's current gen chips.

Despite all of that doom and gloom for the Phenom, its future could get brighter.

AMD demonstrated with the Athlon 64 X2 that it is not afraid to cut prices to compete with Intel, which could improve the Phenom's bang-for-the-buck prospects. And if Intel reduces its prices in response, we could see some very inexpensive quad-core desktops on store shelves next year. You can already get a quad-core system for less than $1,000, and we've heard about new quad-core PCs coming out next year in the sub-$800 range. Do we hear sub-$700...? E-mail to a friend

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