The Elder Scrolls IV: Oblivion
We tested Oblivion by manually playing through a specific point in the game five times while recording frame rates using the FRAPS utility. Each gameplay sequence lasted 60 seconds. This method has the advantage of simulating real gameplay quite closely, but it comes at the expense of precise repeatability. We believe five sample sessions are sufficient to get reasonably consistent results. In addition to average frame rates, we've included the low frame rates, because those tend to reflect the user experience in performance-critical situations. In order to diminish the effect of outliers, we've reported the median of the five low frame rates we encountered.

For this test, we set Oblivion's graphical quality to "Medium" but with HDR lighting enabled and vsync disabled, at 800x600 resolution. We've chosen this relatively low display resolution in order to prevent the graphics card from becoming a bottleneck, so differences between the CPUs can shine through.

Notice the little green plot with four lines above the benchmark results. That's a snapshot of the CPU utilization indicator in Windows Task Manager, which helps illustrate how much the application takes advantage of up to four CPU cores, when they're available. I've included these Task Manager graphics whenever possible throughout our results. In this case, Oblivion really only takes full advantage of a single CPU core, although Nvidia's graphics drivers use multithreading to offload some vertex processing chores.

In raw performance per dollar terms, the Athlon 64 X2 3600+ runs away with this one, followed at a distance by the Core 2 Duo E4300 and Athlon 64 X2 4400+. Quad-core performance per dollar looks pretty dismal in Oblivion, in part due to the fact that the game doesn't actually take advantage of four cores.

Looking over to our scatter plot helps clarify a few things, though. Even at a display resolution of 800x600 with the detail turned down—settings that should highlight differences in CPU performance—variations in frame rate between the chips here are fairly small. We expect those differences to shrink even further once you turn up the detail, at which point performance will really be dependent on the graphics card more than anything.

Considering even the Athlon 64 X2 3600+ can get you an average of 80 FPS (and a minimum of 57 FPS, close to the 60Hz cap on many LCD monitors) in this scenario where the GPU isn't a bottleneck, we wouldn't recommend spending much more on a processor to run this game.

Rainbow Six: Vegas
Rainbow Six: Vegas is based on Unreal Engine 3 and is a port from the Xbox 360. For both of these reasons, it's one of the first PC games that's multithreaded, and it ought to provide an illuminating look at CPU gaming performance.

For this test, we set the game to run at 800x600 resolution with high dynamic range lighting disabled. "Hardware skinning" (via the GPU) was disabled, leaving that burden to fall on the CPU. Shadow quality was set to very low, and motion blur was enabled at medium quality. I played through a 90-second sequence of the game's Terrorist Hunt mode on the "Dante's" level five times, capturing frame rates with FRAPS, as we did with Oblivion.

What we've just said for Oblivion rings even truer for Rainbow Six: Vegas. Here at 800x600, there's a difference of just 13.2 FPS between the $113 Core 2 Duo E4300 and the $1,199 Core 2 Extreme QX6800. Once you turn up the detail, that gap will likely narrow even more. Again, therefore, we wouldn't recommend spending all that much on a processor to run this game. Our FPS-per-dollar chart echoes this: the best value clearly lies with the Athlon 64 X2 3600+ and the Core 2 Duo E4300. (The X2 4400+ can be counted out, since the E4300 offers higher performance for less.)