ThinkBoxly is the personal developer blog of Lucas Chasteen, author, programmer, artist, and always learning. Read more

Saturday, February 27, 2016

GPU Wars: GTX 970 vs 2x GTX 960 in SLI

It's almost upon us: after decades of efforts and dreams, consumer virtual reality won't be a thing of science fiction much longer. In just over a month both the Oculus Rift and HTC Vive will make their debut, and you'll need a pretty decent PC to power them—your graphics card being of particular importance. Both headset manufacturers are recommending an NVIDIA GTX 970 at minimum, and your time to upgrade before the big launch is fading fast. But what exactly will you get for your money if you decide to take the plunge? Let's find out!

Out of the Box...

As the premier 'VR-ready' graphics card, the GTX 970 comes in many shapes and sizes and configurations, creating a sort of low-end, high-end scenario within a single GPU model. For this post I chose to go with an EVGA GTX 970 SSC ACX 2.0 card—which is to say, it ships pre-overclocked and has a fancy cooling system. As a frequent sale item it's one of the most affordable 970s currently on the market, often landing right around $310, so it's a solid option for upgraders—albeit one with a few minor compromises.

As you can see in the unboxing video above, this particular model of 970 checks most of the right boxes. Faster than stock, cooler than stock (that's in degrees, but the slang certainly applies here as well), but what it gains in raw horsepower it loses in practicality—which admittedly isn't much. There's no backplate on this card, the choice of output configuration is unusual to say the least, and at just over 10.1" in length, it's pretty large to boot.

Now that first point isn't a particularly big deal—historically, GPUs haven't shipped with backplates, so even if it is becoming a trend now it's still the norm for the back to be bare. If it really bothers you, you can always buy a backplate separately. But you're stuck with the size and output configuration, the latter of which is particularly puzzling. For this card EVGA elected to include three DisplayPorts and only one HDMI and one DVI-I (which can be adapted to VGA). Now, DisplayPort is kind of like FireWire back a few years ago. It is used by many, and loved by those who use it, but at the same time it's not quite the standard it would like to be. Why is this worth mentioning? For one reason: to use this card with a virtual reality headset, you can't use HDMI for a normal monitor. Of course there are DisplayPort to HDMI adapters aplenty and if you don't need to output audio DVI is equally as good as HDMI, but this factor will give users pause who typically rely on HDMI for other purposes.

On the other hand, though, if the output configuration and physical size of the card aren't a problem to you, EVGA's take on the GTX 970 is a real bang-for-buck deal. At the end of the day a GPU's performance is what counts, and the 970 absolutely delivers.

...And into the Benchmarks

In the past I've compared graphics cards to their last-gen, higher-tier counterparts to give an idea of how performance trickles down to cheaper, more efficient hardware over time. But to really appreciate the 970 I feel it's best to look at things a different way: how it compares to its contemporary brethren. While NVIDIA typically advertises the GTX 960 as their 'sweet-spot' price/performance card, this generation that award really goes to the 970 instead. At $300-350 it's nearly twice as capable as a GTX 960 and only marginally less capable than a GTX 980 which costs almost twice as much. That's to say nothing of a 980ti, which can easily leave a 970 in the dust, but at that point we're practically talking different market categories. The bottom line is, the price versus performance ratio of the 970 is without a doubt the best NVIDIA's Maxwell architecture has to offer, and it also happens to set a baseline for virtual reality that will carry well into the future.

But don't just take my word for it. So you can see for yourself just what the GTX 970 is capable of, I decided to put it to its paces up against two GTX 960s running in SLI. And the results? Well, they're good for the 970 to say the least, but not so much for the competition.

For reference, these tests were run on a system with an Intel Core i5 6600K clocked at 4.0GHz and 16GB of DDR4 RAM.


First up we have my personal favorite benchmark, 3DMark Firestrike. While neither setup can quite handle the test at full speed all the way through, as a side-by-side comparison against dual 960s the single GTX 970 holds up quite well. Many less intense sequences creep near that 60 FPS mark, and plenty of other areas hold close to 30. While you won't want to watch Firestrike in VR any time soon (90 FPS being the standard there) neither is Firestrike your average game, so there's really nothing to be disappointed about here.

In this setup the GTX 970 achieves an overall score of 9,791, while the pair of 960s in SLI fluctuates between 9,600 and 10,400 in different runs—an example of how unpredictable SLI scaling can be, and how it's better to have one high-performance card than two lower-performance ones.

SteamVR Performance Test

Next up we have a new one: Valve's SteamVR Performance Test, built on the new Source 2 engine and featuring scenes from the upcoming Robot Repair Center demo for the HTC Vive. The SteamVR test is a bit different from other benchmarks, as it is designed specifically for VR and uses adaptive fidelity technology to keep framerates above 90 per second at the cost of visual quality. This means comparing FPS directly isn't as important as comparing screen resolution, so you may want to maximize the above video to get a feel for what's really going on. As you'll be able to see, the view on the left (the GTX 960s) constantly flickers and jumps in and out of HD, especially around the edges where this kind of transition and lower fidelity is less noticeable in VR. The right-hand view, however, is significantly more stable and presents a much more consistent level of quality all the way out to the peripheral vision.

Final results award the GTX 960s in SLI with an average fidelity score of 2.8, and the GTX 970 with a vastly superior 6.9. And in case you're wondering, yes, the SteamVR test was utilizing both 960s, however VR currently does not work well with SLI or Crossfire. Case in point: a single 960 on its own scores a 2.7. The moral of the story: while SLI may be viable for VR in the future, that time is not now. Between DirectX 12's explicit multi-GPU feature and vendor platforms like NVIDIA's own GameWorks VR, eventual support for SLI seems inevitable, but on day one single-GPU setups will rule the Rift and Vive. It is worth mentioning that even a single 960 lands squarely in the middle of the Steam VR Test's 'capable' rating, but if you want to do anything more than basic demos a 970 is nothing short of a necessity.

Rise of the Tomb Raider

But benchmarks can only tell us so much, so how about a real-world scenario for a change? Rise of the Tomb Raider has done quite well for itself since releasing on PC a month ago, and is proving to be something of a benchmark in its own right on high settings. For this test I ran the game with a custom configuration: 1920x1080 with exclusive fullscreen and vsync disabled (so as to compare frames above 60 FPS), SMAA, and all settings maxed out except for texture quality, which was set to 'high' to accommodate the 4GB of VRAM on these cards.

Overall the game performs quite similarly on both setups. While the combined strength of two GTX 960s does eek out a slight advantage over an individual GTX 970 you'd be forgiven for getting the two sides of the video above confused. And bear in mind that these are custom 960s with 4GB of VRAM—on a standard 2GB configuration the disparity would be even less, if not tip in favor of the 970 in certain conditions. What this does show is that for traditional 2D gaming going the SLI route isn't a total waste of money. When it works it's actually quite impressive. The downside is simply that it doesn't work 100% of the time to 100% of its full capabilities, as synthetic benchmarks and virtual reality applications painfully show.


In the end the winner here is pretty clear. It's obvious a single GTX 960 can't hold a candle to a 970, and running two 960s in SLI is simply not a reliable or cost-effective alternative, especially when it comes to VR. At peak performance the SLI route may be comparable to a GTX 980 while costing a fair amount less, but until SLI achieves better support it's difficult to recommend. With DirectX 12 that day is surely coming, but until then most gamers will be much better off with a single-GPU solution. Until the next generation of GPUs launches later this year the GTX 970 is hands-down the best option for anyone who wants solid performance at a reasonable cost and is nothing short of a must-have for VR enthusiasts looking to pick up an Oculus Rift or HTC Vive in the near future. Both companies are committed to the 970 as a standard for their headsets, meaning it's still safe to invest in one knowing it will be current for the next few years. As it is the 970's limitations may already be clear, but strap on a headset and dive into a fully immersive virtual world and you'll be sure to forget about them. In the end, if you're still on the fence for how to get your PC VR-ready, get off of it. Until new GPUs arrive, a GTX 970 is the only way to go.