Benchmark Results: CPU Scaling
Looking back at my notes for the Bulldozer launch (AMD Bulldozer Review: FX-8150 Gets Tested), AMD was very enthusiastic about FX’s performance in Battlefield 3 (multiplayer beta, at the time). And no wonder—Battlefield 3's single-player campaign doesn’t care if you’re using a $130 Core i3 or $315 Core i7. It doesn’t care if you come armed with two Hyper-Threaded cores or four Bulldozer modules. It just. Doesn’t. Care.
In fact, after getting a little overzealous swapping out Lynnfield-, Clarkdale-, and Sandy Bridge-based chips, I tried one AMD CPU and decided to call it a day. Any reasonably-modern processor is going to be held back by graphics long before hamstringing performance itself.
How many cores does the game require for optimal performance? With Turbo Boost disabled on our Core i7-2600K, we get all the way down to two cores at the same 80 FPS. Battlefield 3 requires a dual-core chip, though, so with one core left, the game wouldn’t get past its initialization stage.
AMD’s FX-8150 only lets you disable cores in pairs, as Bulldozer modules. So, we slid down from eight to six and four to two, trying to see if this architecture behaves any different from Sandy Bridge. The only slight performance hit happens with one module left enabled, which is seen as two cores. As you can see in the line chart, a handful of hiccups early on in the test are what drag the average down by seven FPS or so.
We’ve also read about folks complaining about stuttering issues caused by Hyper-Threading; disabling the feature seems to smooth things out for them. At no point did a perceptible stuttering (aside from the jerkiness attributable to a too-slow GPU at a too-high setting) afflict our platform. However, we can confirm that turning off Hyper-Threading on the Core i7-2600K, going from eight logical processors to four physical ones, doesn’t hurt performance in any way, and in fact may slightly increase it. The rest of our tests were run with Hyper-Threading enabled, but feel free to shut it off if it benefits your experience!