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System Builder Marathon, Dec. 2011: $1200 Enthusiast PC

FX-6100: A Surprising Processor Bottleneck

We weren't hoping for a miracle in picking AMD's FX-6100 for this quarter's mid-range System Builder Marathon machine. It was almost assured that the Core i5-2500K would beat it (after all, the flagship FX-8150 had a hard enough time with Sandy Bridge at launch).

The real question was whether or not the FX-6100 has what it takes to shift the bottleneck to the dual Radeon HD 6950 CrossFire setup in gaming environments.

The answer, unfortunately, is no. In all but one of the 1920x1080 tests with high detail settings, the stock Core i5-2500K and GeForce GTX 460 SLI combination beats the overclocked FX-6100 with its dual Radeon HD 6950s. In Metro 2033, the one title able to demonstrate an AMD advantage, the result is within 11 FPS.

Perhaps you don't consider our comparison fair because the Core i5 is more expensive. Remember, though, that this configuration costs $200 more than last quarter's, and much of that extra budget went to vastly superior Radeon HD 6950 graphics cards. Even overclocked, the AMD CPU isn't able to match Intel’s stock performance. So, if you want to argue that the $184 Core i5-2300 would make a better comparison, consider that the FX-6100 would still need to be overclocked to 4.5 GHz to match that processor's out-of-box performance. And don’t forget that the Core i5-2300 can be overclocked from its stock 2.8 GHz to 3.5 GHz by forcing the highest single-core Turbo Boost multiplier (it's one of Intel's partially-unlocked chips). Also, think about the FX-6100’s considerable power consumption when it's pushed with all of that voltage.

The landscape isn't entirely bleak for AMD’s mid-range mainstream processor. Load temperatures are quite low, and its overclocking headroom is notable. All of the games we tested were playable, and average frame rates at 1920x1080 never dropped below 36. Really, though, it's hard to come with any reason to recommend AMD's FX over a Core i5 in an affordable build. Certainly, pairing a couple of AMD's very recommendable Radeon HD 6950s with its less-impressive FX-6100 creates platform imbalance.

Still, we’re quite curious to see how this system fares against the rest of the group in our final comparison article at the end of this week. Stay tuned, and remember to enter to win one of our three SBM machines!