Introduction

The Cards

Here at TBG, we've done a number of 4K challenges over the years, starting with the GTX 980 Ti SLI setup, moving on to the GTX 1070 SLI setup, and finally the Titan X Pascal versus the GTX 1080 SLI setup. Well, thanks to the recent release of the GeForce GTX 1080 Ti, Nvidia has pushed gaming performance up a notch, so it's time to benchmark 4K performance on two of these beasts running in SLI.

The truth is that the GTX 1080 Ti is probably the most important release for gamers in a very long time, but coming in the middle of a GPU generation, it's made a bit less of a splash than previous product releases. The fact that it offered a tremendous performance boost over the GTX 1080 at the same price just 10 months later really didn't make as much of an impact as it probably should have. As we found in our GTX 1080 Ti review, it's actually about 30% faster than the GTX 1080, which itself made a gigantic splash upon its release in May 2016 for besting the previous champ, the GTX 980 Ti, by about 30% at a slightly higher price. Comparing these two releases in context, then, the GTX 1080 Ti should have been the bigger deal. But in the end, our guess is that these mid-generation launches just can't garner the kind of attention that big generational shifts do.

Well, we're here to see if enthusiasts should get a bit more pumped about this card, specifically when run in SLI. We're not going to give away the conclusion just yet... read on to find out if GTX 1080 Ti SLI is a must-have for serious 4K gamers!

Test Setup

The Bench

Here are the specs (and a photo) of the system we used for benchmarking:

  1. CPU: Intel Core i7-6900K, overclocked to 4.3GHz
  2. Motherboard: Asus X99-Pro/USB3.1
  3. Video Cards: 2x EVGA GeForce GTX 1080 Ti 11GB Founders Edition
  4. SLI Bridge: EVGA High-Bandwidth SLI Bridge 1-Slot
  5. RAM: Corsair 4x8GB Vengeance LPX DDR4-3200
  6. SSD #1: Samsung 950 Pro M.2 512GB 
  7. SSD #2: Samsung 850 Evo 1TB
  8. Case: SilverStone Primera PM01 
  9. Power Supply: EVGA Supernova 1000 PS 
  10. CPU Cooler: Corsair Hydro H100i v2 
  11. Operating System: Windows 10
  12. Monitor: LG 27UD68-P 27-Inch 4K 

Note that we'll be providing benchmarks for our 1080 Ti SLI duo at both reference and overclocked speeds. As with all Pascal cards, overclocking headroom of the GTX 1080 Ti is fairly limited; we were able to increase the core on our two samples by 160MHz (about 9%) and memory to 11,800MHz (up 7% from the reference 11,000MHz). Remember, when running in SLI, both cards must remain stable, so while one of our cards had a bit more headroom, we were limited by the lesser of the two samples. You can actually run them out of clock sync, but we don't see that as being worthwhile. We ran our +160MHz/+800Mhz clocks in every single one of our games, and they never crashed a single time, but definitely crashed if we tried to push them any higher. We're always suspicious of overclocking claims, even those done by professional reviewers, when the results are shown for just one or two games. That, dear readers, does not a valid overclock make!

To eliminate system bottlenecks as much as possible, we used our X99-based benchmarking system, which features an Intel Core i7-6900K processor was overclocked to 4.3GHz. As we found in our gaming CPU shootout, in many games, the extra power of this eight-core processor is critical to getting the most out of a high-end GPU configuration. For our testing, we're using one synthetic benchmark and eight games, all running at a native 4K resolution: 3DMark Fire Strike Ultra, Crysis 3, Far Cry 4, The Witcher 3, Fallout 4, Rise of the Tomb Raider, DOOM, Battlefield 1, and Watch_Dogs 2. Each game was run with the highest preset available, typically referred to as "Very High" or "Ultra." Note that in every game other than Battlefield 1, this is actually not the highest setting available, as individual parameters may have additional quality settings beyond Ultra, for example DOOM has a few "Nightmare" settings, and a number of games have extra ambient occlusion settings that aren't included in any preset. For the sake of making comparisons easy, we decided it wasn't worth it to max out each individual quality setting.

All game data was collected in actual in-game runs, which often provide totally different (and obviously more relevant) results than canned benchmarks. We used FRAPS to collect data for three 30-second samples of each benchmark on each video card setup. And take note: as always, we bench Battlefield 1 in a multiplayer round, which performs far differently from the single-player game that nearly ever other review site benchmarks but no one actually plays! Trust us when we say that getting reliable data in live BF1 matches takes almost as long as collecting all the other data combined, which is why you rarely see it done! We tested only at 4K because we truly believe that if you're spending this much money on video cards, you should be gaming on a high-end monitor, which today means either 4K/60Hz or 1440p/100+Hz. As a rule of thumb, 2560 x 1440 runs twice as fast as 4K, so if you can hit 60fps at 4K, you can hit a high-refresh-friendly 120fps at 1440p. Have a 1080p monitor and want a GTX 1080 Ti? Get a new monitor first, please! As you'll see, GTX 1080 Ti SLI is arguably too fast even for 4K!

OK, now that we've explained the method to our madness, it's time to move on to the results!

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