Frame Rating: GeForce GTX 660 Ti and Radeon HD 7950
Crysis 3 (DirectX 11)
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Crysis 3 starts out much in the same way that Battlefield 3 did - CrossFire looks much different in FRAPS than it does in our Frame Rating-based observed FPS result.
The reason is pretty simple to understand when you view a frame time graph like this. The single HD 7950 does outperform the GTX 660 Ti by a small margin but with SLI's smoother multi-GPU result makes a dramatic impact for anyone that might be considering pairs of either card.
The minimum FPS percentile information shows another view of performance where the SLI result is obviously the only one that scales with two GPUs. The GTX 660 Ti cards goes from about 25 FPS (total run average) to nearly 45 FPS. While both single cards have consistent frame rates you can see the sudden drop off at the end for SLI.
Interesting results here - the HD 7950s in CrossFire are clearly the most troublesome with the frame time variances. The GTX 660 Tis in SLI also show more variance than the single cards after the 90th percentile but it is much less dramatic than the 20+ ms jumps you see from AMD.
While all card performance starts to fall off at this resolution and these quality settings, the same problem persists with the HD 7950s in CrossFire.
With a slower frame rate due to performance issues, the problem of AMD's CrossFire gets worse as we see frame times alternate between ~5 ms and ~85 ms! SLI does have some hitches and spikes in frame times as well and only the single Radeon HD 7950 3GB card can run through without a problem. Obviously the 2GB vs 3GB frame buffer is starting to make a difference in Crysis 3 at Very High settings.
While the GTX 660 Ti definitely scales going from one card to two, the frame rate definitely starts to drop towards the end of the graph, and more suddenly than we would like. Looking at just the single GPU cards, the Radeon HD 7950 starts out with an average just a couple of FPS higher than the GTX 660 Ti but it stays about that much faster throughout our test.
Our 2560x1440 frame variance results again paint the HD 7950s in CrossFire in another negative light with frame time variances that are high from beginning to end. Note that the GTX 660 Ti, in both single GPU and SLI configurations, actually has more variance than we would like at these settings as well with only the Radeon HD 7950 keeping things within check.
Things aren't looking pretty for any of these cards at 5760x1080 at these quality settings - future runs will likely be run at lower IQ options. We still see a ton of dropped frames from the AMD Radeon HD 7950 CrossFire config.
Both CrossFire and SLI show some varied frame times in our plot here though CrossFire continues to look much worse with a lot of frame occillation. The black line, slightly hidden by the SLI result, is clearly the best performer.
Interestingly, even the GTX 660 Ti in SLI can't really keep up with the results of the single HD 7950 that puts in the most consistent work. At about the 85th percentile the GTX 660 Ti SLI results actually fall below that of the single GTX 660 Ti and the CrossFire HD 7950s. This is definitely showing the cases where gaming scenarios that are heavily limited by the CPU and other factors can be bottlenecked in other ways.
The Radeon HD 7950 3GB is definitely the best option of the four card configurations tested here with both CrossFire and SLI resulting in high variance levels.