Let me start with what this article is not about. It's not about value. It's not about mainstream (or even enthusiast) gaming. It's not about comparing AMD and Nvidia.
Now that official support for three- and four-way SLI in games is gone, this article is about the pinnacle of performance achievable in late 2016 with Nvidia's Pascal architecture, assuming money is no object.
This article is also about tinkering with really high-end hardware, trying to overclock two Titan Xes in SLI, seeing how they fare in VR, and testing whether the lack of HBM2 (Nvidia opted for GDDR5X instead) is a big deal.
Anyway, I've done the multiple card setups for many generations, but game development is going in a direction where that's no longer a worthwhile endeavor as support dwindles more and more.
Thanks for the read.
When I got my 1080's I tried the EVGA bridge and had problems with getting full contact on my cards. Some boots would show the cards, some didn''t, so for a time I used dual ribbons until I got the NVidia HB a week or two later. The NVidia worked for me no problem. The main difference I noticed was, a few more FPS here and there but really a more stable, consistent frame rate. I read the same article about the x-ray comparisons as well before purchasing and have to say all this info is getting pretty consistent.
I can tell you that 1080SLI has very similar performance behavior as to the reviews of Titan X SLI I've seen. Both SLI setups seem to really shine in the 4k/60hz or 1440p/144hz. When I tried DSR 5k on my 4k display the frames quickly dropped to around 40fps.
I'm not really seeing the CPU bottleneck you mention except for the Firestrike tests. Whether 4k/60hz or 1440p/144hz my 4930k @ 4.10ghz rarely goes above 40%.
I completely agree with you about what to use the Titan's for- 4k/5k all the way. 1080SLI just starts to hit a ceiling at around 60-80fps in 4k and averages 100-150fps in 1440p depending on the game.
I have an acer X34 monitor so 3440 x 1440, my PC is running a i7-6700k at stock speed. I keep thinking about blowing another $1200 just to go SLI just because "moar is moar" and just the thought of Titans in SLI give me a nerd boner, but it honestly seems like I'd see no noticeable benefit.
Since you noticed two Titan XP's achieving only 50% utilization when paired with the i7-6700k, then which overclock CPU would diminish or eliminate that condition? i7-5820k (CPU I own) or an i7-5960X? Any other recommendations would be appreciated. Thank you for the great article.