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What would you recommend for rendering on GPU (iray, V-Ray RT, VRED) and doing some VR; two GTX 970 or one GTX980 Ti card? I can get these setups for roughly the same price.

  1. Cuda cores

    • 970: 2x1664 = 3328

    • 980Ti: 2816

  2. VRAM

    • 970: 4GB

    • 980Ti: 6GB

  3. Memory Bandwidth

    • 970: 224 GB/sec

    • 980Ti: 336.5 GB/sec

  4. Texture Fill Rate

    • 970: 109 GigaTexels/sec

    • 980Ti: 176 GigaTexels/sec

I know that the memory in two 970 does not add up to 8gb in total, so two 970 will give me less VRAM. But what about the total number of CUDA cores compared to the lower amount of VRAM and lower memory bandwidth?

My motherboard has 3x PCI Express 2.0 x16 slots with support for 3-way SLI. I also have my old GTX 590, that I was thinking of keeping for Windows to work with.

Cheers!

  • 1
    My advice to you is to wait for nVidia's next generation GPUs. Since it is not released and their are no reviews yet, this is a comment and not an answer, but check out the rumored specs on the page compared to the 980TI. – Cfinley Mar 24 '16 at 14:09
  • Wow, that's some fascinating specs! Thanks for the info. Not sure I can wait that long though, might need something next month already. – Kristoffer Helander Mar 24 '16 at 14:24
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As has been said, Pascal is coming soon, and is expected to have greater performance increases than the Kepler to Maxwell transition (Pascal should be released to public around the end of Q2). However, I wouldn't dismiss multi GPU setups out of hand, though perhaps it makes more sense as a later upgrade.

Why multiple GPUs are better with Pascal:

  • Pascal Introduces NVlink, which can be used to connect GPUs even when the CPU does not support it as in the image below (image source)

NVlink

  • Rendering generally scales well with multiple GPUs. SLI is not required.

(sources: iray benchmarks, VRED Nvidia article, Vray RT Nvidia article)

  • With the introduction of DirectX 12, Split Frame Rendering is making a comeback. Multiple GPU solutions with good game support can have comparable frametime latencies and also allows the graphics cards to not duplicate all the resources across the two memory pools.

Why you might opt for a single GPU anyway:

  • Upgradability. You could always drop in a second later. Third GPU scaling is way worse, though that might change with NVlink, a single GPU is still the better option in that respect.
  • Support. It's annoying when sometimes SLI doesn't work for a game, and you're stuck with poor performance. You'd also need a slightly bigger PSU and case, because lower end cards are higher clocked, and two obviously take more space.

What you should also consider:

AMD's Polaris is also releasing around the same time, and is supposed to have competitive performance per watt. Of course, you might run into problems with vendor specific software, such as those using CUDA, but it goes both ways (well, slightly more in favor of Nvidia, owing to their market share), and AMD hardware generally have better OpenCL performance. If you're not worried about power consumption and you want your computer now, 2 R9 390s would be decently better performing than 2 GTX 970s at high resolutions.

| improve this answer | |
  • Thanks for all that information, that was fantastic! I am mostly concerned with rendering (iray, mental ray) and physics simulation on the GPU (PhysX) and those relay heavily on CUDA. I think I will wait for the Pascal series of cards, if only for the price of Maxwell cards to go down. Perhaps I can save up for two discount 980 Ti! :) – Kristoffer Helander Mar 27 '16 at 23:50
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Well, just like @Cfinley said, Nvidia is about to drop the Pascal Series. You're probably get the most bang for you buck with one of those, but since we don't have concrete prices/specs, it's mostly just speculation. If you want your GPU soon, I would recommend the 980 TI over 970 SLI. In my opinion, there are many benefits to the 980 ti.

  • Lower TDP. The 980 TI has a TDP of 250, whereas the 970 SLI has 290.

  • SLI is not always supported. This varies from program to program and game to game, but a single card is more reliable.

  • Most benchmarks I can find show the 980 TI getting a higher framerate. Here's an article. I don't know how well this transfers when you're rendering rather than gaming, but I'd assume the one that's better for gaming is also better for rendering.

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  • Thanks for the information about TDP, I never heard of that before. I think I will wait a while and see what the Pascal Series has to offer. If nothing else, perhaps at least the price for 980 Ti will drop low enough so I can afford two of those instead. – Kristoffer Helander Mar 27 '16 at 20:44

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