Preview: NVIDIA GeForce GTX 1080 SLI benchmarked

Note: This article was first published on 24th May 2016.

Does 1 + 1 = 2?

NVIDIA’s new flagship graphics card, the GeForce GTX 1080, sounds like every gamer’s dream. As the first consumer card to finally break free of the deadlock of the 28nm process node, the card demonstrated the efficiency of the 16nm FinFET process right from the outset, with stellar power consumption figures and performance that put the GeForce GTX Titan X to shame.

And if one card is already so powerful, how about two of them in SLI? Before we dive into our preliminary results, we’d like to touch briefly on the changes NVIDIA has made to the way SLI is handled with its Pascal GPUs. As we noted in our review, NVIDIA will now officially support only two-way SLI going forward, largely due to the difficulty of deriving meaningful performance scaling improvements in three- and four-way configurations. Not that it wouldn't work, but it's more about NVIDIA not having to officially test and certify content, drivers and the graphics card for such insane configurations that are usually reserved for only breaking records.

In addition, NVIDIA also introduced a brand new type of high bandwidth SLI bridge that it has dubbed SLI HB. This bridge facilitates high-speed data transfers between SLI interfaces by linking both connectors in a dual-link SLI mode that offers more than double the bandwidth of older bridges. More specifically, the new SLI interface runs at 650MHz, as compared to 400MHz in older GeForce graphics cards using the legacy bridges. This allows the SLI HB bridges to take advantage of Pascal’s higher speed /IO, and enables users to better maximize performance at 4K resolutions or higher.

In fact, NVIDIA says that certain older SLI bridges – custom bridges with LED lighting to be specific – will also be able to operate at 650MHz when used with the GeForce GTX 1080.

With that said, the GeForce GTX 1080 will still work with legacy bridges, although NVIDIA says the GPU will be limited to the maximum speed of the bridge being used. In the end, we used a couple of bridges that shipped with MSI’s new X99A Gaming Pro Carbon motherboard to get an idea of what sort of performance to expect from two of these monster cards in SLI. Bearing in mind that performance could very well be better if used with the proper bridges, here’s a look at some of the figures we obtained.

Test Setup and Results

We used the same test rig as we did in our review. The specifications are as follow:

Intel Core i7-5960X

ASUS X99-Pro (Intel X99 chipset) motherboard

2 x 4GB Corsair Vengeance LPX DDR4-2133 (Auto timings: CAS 15-15-15-36)

Samsung SSD 840 Pro 256GB SATA 6Gbps solid state drive (OS + benchmark + games)

Western Digital Caviar Black 1TB SATA 6Gbps hard drive (general storage)

Windows 10 Pro 64-bit

Intel INF 10.1.1.14

As it turns out, these figures aren’t too bad at all. In fact, NVIDIA hasn’t exactly advised against using the older bridges, and it says that the standard bridges are actually okay for use with games running at more modest 1080p or 2,560 x 1,440-pixel resolutions. The HB bridges will instead come in handy for refresh rates 120Hz or higher, or at 4K resolutions and above.

That explains the large jumps in performance we saw at certain settings, like the whopping 81 percent jump in Middle-earth: Shadow of Mordor at 1600p. In The Division, there was also a 45 percent boost at the most demanding settings and resolution.

However, it wasn’t all smooth sailing, and we also noticed oddities like inconsistent performance in Ashes of the Singularity (DirectX 12 mode), where the SLI setup displayed virtually no improvement at High settings, even evidencing a performance drop at 1080p resolution. On the other hand, at Crazy settings, there was a 52 percent jump from a single GeForce GTX 1080.

Furthermore, there were virtually no improvements when running the game in DirectX 11, which is why we’ve chosen to omit the results here. Similarly, Hitman failed to produce any performance gains in either DirectX 11 or 12, so it looks like SLI performance is patchy at best for now. Still, this could be due to any number of factors, from the legacy bridges to the beta drivers that we used, but we're hopeful that these issues will straighten themselves out in the form of driver updates when the card launches on 27th May.

