Multi-GPU solutions with Bulletstorm
We still need to address some additional issues related to multi-GPU stuttering, but before we do so, I'd like to get the results from a couple more games under our belts.

Next up is Bulletstorm, which we tested in a different fashion than Bad Company 2. Rather than attempting to duplicate all of the exact same motions in each test run, we simply played the same level of this game through five times, in 60-second sessions. That means we have more variance in our results for this game, but with five runs worth of data, we should be able to make some assessments anyhow.

Here's a look at frame time data from a single test run for each config.

You'll notice that in this game, most of the multi-GPU solutions' results look more like lines than clouds. The biggest exception is the Radeon HD 6870 CrossFireX setup, which still appears to exhibit quite a bit of jitter.

The other big difference here is that there are quite a few more spikes up to 40 ms or more during the test runs. The worst offender is the GeForce GTX 560 Ti SLI config, which performs poorly throughout. Our guess is that these 1GB cards are running low on total memory, which is why they struggle so mightily. Yes, the 6870 cards also have 1GB, but AMD has long been better at avoiding memory size constraints.

Get your mouse wheel ready, and we'll zoom in on a snippet of this test run from each config.

For whatever reason, multi-GPU jitter is much less pronounced here. In fact, it's nearly banished entirely in the case of the GeForce GTX 580 SLI and Radeon HD 6970 CrossFireX configs. Remember, this is just a small selection of frames from a single test run, so it's not the whole story. Still, from looking at the full data set, my sense is that these samples are fairly representative of the amount of jitter throughout each run and from one run to the next. Of course, frame times will vary depending on what's happening in the game.