Battlefield 3 multi-GPU performance
Let's take a look at another game where multi-GPU micro-stuttering comes into play. This time, we've left out the Fraps numbers so we can concentrate on both raw and filtered FCAT results.
Obviously, the Radeon HD 7970 CrossFire setup cranks out more frames than anything else in this test, but just as clearly, it has some pronounced jitter going on. Here's an extreme close-up of some of the worst of it:
FCAT's filtering removes those runt frames from the equation, and we're left with substantially altered performance results for the CrossFire rig. As you can see, none of the other solutions' results are affected at all. Their filtered and raw frame time plots and latency curves entirely overlap, and the rest of their scores are identical.
With the FCAT filtering applied, the Radeon HD 7970 CrossFire setup's average FPS drops precipitously. Even without filtering, the longer frame times in its jitter pattern affect its latency curve negatively. Add in filtering, and the CrossFire rig's 99th percentile frame time drops back to match a single Radeon's almost exactly. Filtered or not, there really is no measurable benefit to having a second graphics card in the mix.
With that said, we have to point out that in this game at these settings, the 7970 CrossFire rig performs just fine, speaking both subjectively and going by the resulting numbers. In our measure of "badness," time spent working on frames beyond 50 milliseconds, none of the cards register even a single blip. They spend no substantial time working on frames that take longer than 33 ms, either.
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