The Elder Scrolls V: Skyrim
Our test run for Skyrim was a lap around the town of Whiterun, starting up high at the castle entrance, descending down the stairs into the main part of town, and then doing a figure-eight around the main drag.
Since these are pretty capable graphics cards, we set the game to its "Ultra" presets, which turns on 4X multisampled antialiasing. We then layered on FXAA post-process anti-aliasing, as well, for the best possible image quality without editing an .ini file. We also had the high-res texture pack installed, of course. Although it's not pictured above, the total display resolution was 5760x1200.
These first three plots show the raw data from a single test run, the rendering times for each individual frame, shown in milliseconds. Notice that because we're thinking in terms of frame latency, lower numbers are better. For reference, we've included a table on the right showing the conversions from frame times to FPS.
As you can see, the GTX 690 performs essentially identically to two GTX 680s in SLI. Throughout the test run, the GTX 690's frame latencies remain below 22 milliseconds or so, and they're often under the magical 16.7 millisecond mark that, if it's steady, translates into 60Hz or 60 FPS. Some of the other cards don't fare as well, especially the Radeon HD 6990, whose spike-riddled plot reveals frame times that are often rather high. The GTX 590's plot looks more like a cloud than a line, suggesting that it has some jitter going on, as well.
Just looking at the FPS average, the GTX 690 ties the GTX 680 SLI team, well ahead of anything else. Two Radeon HD 7970s in CrossFire, surprisingly enough, aren't any faster than a GeForce GTX 590.
Of course, we've established that FPS averages don't tell the whole story. We can get a better sense of the overall frame latency picture by looking at the 99th percentile frame time. Simply put, for each card, this number means that 99% of all frames were rendered in x milliseconds or less. Since we're looking at a point where the vast majority of frames have been completed, the effects of any micro-stuttering oscillations will be reflected in this result.
Switching to this more latency-centered indicator does some interesting things for us. First and foremost, it brings the GTX 690 and the GTX 680 SLI back to the pack. Those two are only a couple of milliseconds ahead of a single GTX 680 in this measurement. Oddly enough, the Radeon HD 7970 CrossFire config looks to have higher latencies at the 99th percentile than a single 7970 card does. Worst of all for AMD, the Radeon HD 6990 looks like a basket case. Going by FPS alone, the 6990 would appear to be just a few ticks behind the 7970. A look at the latency picture reveals the gulf between the 6990 and everything else.
Then again, 99th percentile frame times are just one point along a whole latency curve, and we can show you how that curve looks.
With multi-GPU products in the mix, these latency curves are more interesting than ever. You can see that the GTX 690 and the 680 SLI config are evenly matched throughout the test run, with no real weaknesses. Both solutions deliver frames quickly throughout, although their frame latencies rise, nearly to meet the single GTX 680's, in the last 5% of frames.
The curve for the Radeon HD 7970 CrossFire setup tells quite the story. Although the dual 7970s deliver half of their frames much more quickly than a single card, their frame times rise at a sharper angle beyond 50%, eventually crossing over at around 82-83%. For the last 16% or so of frames delivered, the single Radeon HD 7970 is quicker. We're likely seeing two halves of a multi-GPU jitter pattern illustrated in the 7970 CrossFire's more rapidly ascending curve, and in the final analysis, the single 7970 may be the better of the two solutions.
We can also quantify "badness," the slowdowns and delays one encounters while playing a game, by looking at the amount of time spent rendering frames above a certain threshold. The theory here is that the more time spent on long-latency frames, the more interruption you're likely to perceive while playing a game.
We've chosen several noteworthy thresholds. The first, 50 milliseconds, equates to 20 FPS. We figure if the frame rate drops below 20 FPS for any length of time, most folks are likely to perceive a slowdown. The next two, 33.3 ms and 16.7 ms, equate to 30 and 60 FPS, respectively, which are traditionally important performance thresholds for gamers. Our three thresholds also equate to 60Hz, 30Hz, and 20Hz, the first three quantization points for a 60Hz display with vsync enabled. If you go beyond any of these points, you'll be waiting at least one more vertical refresh interval before updating the screen.
As you might have expected, only the Radeon HD 6990 suffers any really substantial slowdowns, and even it doesn't waste too much time working on frames above 50 milliseconds.
When we ratchet the threshold down to 16.7 ms, the GTX 690 and 680 SLI really separate themselves from the pack. A single GTX 680 card spends about three times as long as a GTX 690 or two GTX 680s in SLI above 16.7 milliseconds—so in a really picky way, the GTX 690 is measurably better at minimizing wait times for those worst-case frames.
Notably, the Radeon HD 7970 single-card and CrossFire configs are essentially tied here. Adding a second Radeon doesn't appear to help at all in the most difficult cases.
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