Frame Rate-Over-Time Analysis
Our first article included a frame rate-over-time analysis intended to identify problematic sequences in our testing. Regardless of whether you're using one card or multiple GPUs, dramatic slow-downs interrupt game play. Unfortunately, although Nvidia enabled Don (up in Canada) and Chris (down in Southern California) with its FCAT tools, I'm only able to use the Fraps-based testing I ran previously. We know from our comparisons in Challenging FPS: Testing SLI And CrossFire Using Video Capture that Fraps isn't able to accurately capture the dropped and runt frames that might plague one graphics solution but not the other. However, we are at least able to track when each combination of cards drops to levels we deem unplayable.
Our least-demanding Battlefield 3 settings should reveal CPU bottlenecks, and indeed we see that three out of four multi-GPU configurations turn in similar results. Only Intel's Core i7 is powerful enough to butt up against the game’s 200 FPS cap, and only when it’s paired with two GeForce GTX 680s in SLI.
Our most taxing settings should demonstrate GPU limits. Unfortunately, those limits appear fairly consistent for all four dual-GPU configurations. At least the test runs smoothly, staying well above 50 FPS throughout its duration.
An attempt to demonstrate CPU-bound conditions in Skyrim is somewhat successful, with noticeable separation between the Intel and AMD CPU results. Both processors favor SLI over CrossFire in this title.
And now for our most taxing detail settings in Skyrim, where graphics performance matters most. Two Radeon HD 7970s in CrossFire beat the GeForce GTX 680s in SLI on the Intel-based system, while the reverse holds true for AMD's FX-8350. Doh!