As always, we start with baseline data from 3DMark, which is useful to confirm that SLI is working, and also provides some goalposts for what to expect in terms of SLI scaling.
In this graph, focus your attention on the orange bars. They signify the Graphics Score, which is what we really care about when it comes to the performance of the GTX 1070 video cards in our systems. Note that in a single-card configuration, the 6700K on the Z170 platform acutally outperforms the 6900K on the X99 platform by about 1.5%. That's within the margin of error, but when looked at in tandem with the dual-card configurations, where the 6900K on the X99 board wins by 1%, we start to see a hint of the benefits of more bandwidth. Remember, when using a single card, both platforms can provide 16 PCIe lanes. Double up on cards and the 6700K can only provide 8 lanes to each card. That, in a nutshell, is why we see the flip in the standings.
Looked at another way, in terms of PCIe efficiency, the 6700K allows 90% scaling when jumping from one card to two, while the 6900K allows 95% scaling. Remember, this is not CPU limited, it's chipset limited. While the 6900K can put out a massive amount of Physics performance, that doesn't affect the Graphics Score.
3DMark Time Spy
Time Spy is a sign of things to come in PC gaming. Its advanced graphics engine has monumentally more draw calls than Fire Strike. According to 3DMark, this new benchmark throws five times more graphics content at the system to process. So while the 6700K only allows our GTX 1070 cards to offer a 72% boost in SLI, the 6900K allows 85% scaling in SLI. That means we see a virtual tie with a single 1070 to the 6900K being 7% ahead in SLI.
Note that due to the complex ways in which DirectX 12 allows this kind of jump in performance, we aren't quite sure whether the Graphics Score is affected by CPU power. We'll be doing more CPU-centric testing in the near future to try to determine exactly what's at the heart of performance in Time Spy.
Crysis is as close to a universal PC benchmark as we've ever seen in an actual PC game. That was true of the original Crysis, a bit less so in the console-focused Crysis 2, but Crysis 3 was another game-changer, so to speak, when introduced in 2013. It was so forward-looking that no system could come close to maxing it out at 1080p when it was released. And yet, now we have a configuration that can max this game out at 4K and make it look and play great! Indeed, this game engine is so smooth that you don't need more than 40 frames per second to have an ultra-responsive gaming experience.
And interestingly, while this game has traditionally been CPU limited at high settings when running at 1080p or 1440p, pushed to a GPU-crushing 4x MSAA at 4K, nothing but the GPU matters. So our powerful 8-core X99-based system doesn't get a leg up on its cheaper cousin. The two systems are tied with a single card, and are essentially tied with dual cards as well. We're a bit surprised that the higher bandwidth available on the 6900K platform doesn't yield any benefits here, but that may be because the bottleneck at the settings we used isn't PCIe bandwidth but rather GPU processing power.
All right, let's now take a look at a handful of other popular PC games to see how our platforms perform when hit with a 4K gaming load.