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AMD Phenom II X6 1090T And 890FX Platform Review: Hello, Leo

Intel’s Core i7-980X gave us a six-core processor running at the same speed as its predecessor with a shared L3 cache increase to boot—and all at the same price point. Unfortunately, at $1,000, it’s still hard for most folks to get excited about hexa-core computing. If you can afford a grand, great. The -980X remains the fastest desktop processor available, and it sells at the same price as the quad-core -975. Choosing between the two is a no-brainer.

AMD took a different approach, adding cores (and corresponding L1/L2 cache), but leaving the shared L3 at 6MB. The addition of Turbo CORE shoots to emulate what Intel achieves through Turbo Boost, but it’s effectively Cool’n’Quiet in reverse, and arguably not nearly as elegantly implemented. Moreover, a $100 price increase means you’ll be paying more for AMD’s six-core solution.

But the Phenom II X6 1090T costs $295 to the Phenom II X4 965’s $185. This is a six-core CPU most of us can actually afford. The question is: who should spend the extra money?

Four Or Six?

The benchmarks speak volumes in this story. The moves from one to two cores and two to four were each met with slight clock rate drops, conceding to the increased complexity of doubling execution resources. Each step of the way, gamers actually saw better performance from the higher-clocked one- or two-core processors, while the folks using threaded software watched performance spring forward thanks to parallelism.

It might have been a fluke that Intel was able to time its 32 nm die shrink with the launch of its six-core Gulftown, but that was actually the first time I can remember that no compromises were made in increasing core count. AMD doesn’t have that luxury. The addition of low-k dielectric material in the metal layers almost amazingly facilitates a six-core design within AMD’s 125W TDP, but it’s not enough to kick the clocks up another notch.

As a result, it’s easy to recommend the Phenom II X6 1090T for folks able to employ its six cores. Video work, threaded Photoshop filters, rendering—in those workloads, AMD’s new flagship is, in many cases, able to keep up with the quad-core Core i7-975.

In the same vein, the gaming benchmarks are a reminder that the latest and greatest graphics cards really do need a capable processor behind them if you want to unleash their potential. An overclockable CPU like the Core i7-920 or -930 can really open up a Radeon HD 5870 or GeForce GTX 480 when you get it up to the 4 GHz range. Dipping down to 3.2 GHz doesn’t really help the 1090T win any battles in the games (Call of Duty excepted, where Turbo CORE seems to improve performance over the X4 965). If you’re a gamer, save the money you’d spend on a six-core CPU, buy your favorite overclockable processor, and spend the difference on graphics or an SSD to cut level load times.

AMD’s hexa-core Phenom II X6 1090T is decidedly a productivity-oriented part designed to improve the performance of threaded apps. It extends the usefulness of Socket AM3 until Bulldozer emerges in 2011. As a result, your 790FX-based motherboard will do the job just fine—it’s probably not worth upgrading to 890FX at this point. Turbo CORE is conceptually a good answer to Turbo Boost, but I had a hard time proving its effectiveness in the real-world. Best-case, it helped the 3.2 GHz 1090T keep pace with the 3.4 GHz 965 in single-threaded titles.

Perhaps the most impressive point from this launch is the fact that AMD is increasing core count by 50%, transistor count by just under 30%, and maintaining the same 125W of its fastest quad-core CPU. It’s almost a shame that price increases by more than 50% at the same time. Fortunately, there are plenty of heavily-threaded workloads that justify a sub-$300 six-core CPU.

Update: AMD just let me know that is offering a $50 mail-in rebate on both the 1090T and 1055T processors. This improves both processors' values significantly, but especially makes us think long and hard about the Phenom II X6 1055T, which can now be had for less than the Phenom II X4 965, our real benchmark in this story. For as long as the Tiger deal lasts, its savings add quite a bit more impact to AMD's hexa-core launch.

Update2: Looks like the plug has already been pulled on the rebate.

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