SLI Scaling In Game Benchmarks
We're deliberately trying to be balanced with our game selection by including an AMD "Gaming Evolved" title (Thief), an Nvidia "The Way It's Meant to be Played" game (Middle-earth) and a couple of titles not specifically affiliated with either vendor (BioShock Infinite and Elite Dangerous).
All benchmark results are averages of three separate runs. Variation was minimal (<1%) across them.
Scaling at 2560x1440 (1440p) varies between 60% and 69% in these tests. In many cases, however, we find ourselves CPU-limited. The lack of scaling isn't due to any particular issue with SLI as a technology, but rather the fact that our Core i7-4770K at 4.4GHz can't keep up with the GeForce GTX 980s!
Nevertheless, with average frame rates between 97 and 150, all of these games look exceptionally smooth on the 144Hz display we used to test, even with G-Sync disabled.
Scaling at 3840x2160 is even better than 1440p, varying between 75% and 84% in these tests. At this punishing resolution, the frame rates go down and we're no longer CPU-limited. The GPUs are bottlenecking performance, as evidenced by utilization numbers hovering close to 100% throughout our benchmark runs.
As you can see from our data, a single GeForce GTX 980 is sufficient for playable performance in these games at their highest quality present under the following conditions:
- At 1440p: Allows for what we could call a decent experience. On average, performance falls between 50 and 80 FPS, which is enough to play smoothly with v-sync disabled or with a G-Sync-capable display.
- At 2160p: Allows for what we could call a barely playable experience. On average, performance falls between 28 and 45 FPS, resulting in many sequences falling below 30 FPS and, overall, gameplay that just doesn't feel smooth.
Adding a second GeForce GTX 980 in SLI facilitates the following benefits:
- At 1440p: Allows for v-sync to be enabled with no stuttering on 60Hz displays, or for even smoother gameplay on 120/144Hz displays with performance averaging between 97 and 150 FPS.
- At 2160p: Allows for what we could call a decent experience, with performance averaging between 50 and 83 FPS. That's enough to play with v-sync disabled, though based on testing we'll present shortly, you'll still have to live with micro-stutter in some cases.
In short, while a single GeForce GTX 980 is more than sufficient to drive a 1080p/60Hz display in almost any scenario, adding a second card in SLI introduces benefits to anyone who owns a 1440p/60Hz display or higher, with the gains most pronounced for those playing on 4K screens or enabling 120/144Hz refresh rates. At 4K, SLI is essentially a requirement for a decent experience, although the problem of micro-stutter has not been solved entirely yet for SLI at this resolution.