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How bottlenecked would a PCIe 3.0 x16 card be in a 2.0 8x slot?

My motherboard has one only PCI Express 2.0 x16 slot and two PCI Express 2.0 x8 slots.

I would like to SLI two GTX 760's, but how bottlenecked is a PCIe 3.0 x16 card going to be living in a 2.0 x8 slot? Would I get better performance from a single GTX 780 instead of SLIing the 760's in this case?

Processor is a i7-980 Gulftown 3.33GHz Six-core, so I should be fine there.
4 answers Last reply Best Answer
More about bottlenecked pcie x16 card slot
  1. You will see no bottlenecking at all with 2 x GTX 760s in your PCI-E 2.0 x8 slots. Now I have not read up on GPU scaling on PCI-E generations since the GTX 680 was the flagship card so with an R9 290X, GTX 780 or Titan there might be a slight bottleneck but as of my last reading on the subject the PCI-E standard was well ahead of what is necessary for even high end graphics cards.
  2. Best answer
    I'd have to look up the data, but I don't think you'd be bottlenecked in that scenario, or if you were it would be quite small. I know a single HD7970 or GTX680 didn't max out a PCIe v2.0 x16 slot. My gut tells me there's be a SMALL amount of bottlenecking in some scenarios such as 5%.

    However, while SLI has improved it's still not as smooth as a single card. My advice is THIS card:

    EVGA GTX780 3GB (the 967MHz Base Clock model). It's $500.
    http://www.newegg.com/Product/Product.aspx?Item=N82E16814130918

    BENCHMARKS:
    http://www.guru3d.com/articles_pages/evga_geforce_gtx_780_classified_review,20.html

    *No 760 SLI in this list. You can estimate though by averaging say 70% improvement. Performance by this estimate is thus the SAME except you have:
    - less RAM for 760 SLI
    - more NOISE for 760 SLI
    - way less performance when SLI doesn't work, or when the driver support isn't optimized
    - microstutter (not the problem it was but a single GPU is smoother)
    - about the SAME price for 2x760 SLI as a single EVGA 780.

    Summary:
    I can find no good reason to get 760's in SLI now that this awesome EVGA 780 card is $500 and is better in every way.

    *Battlefield 4 will use more than 2GB when you crank up the quality. SLI clones data between cards so 2x2GB is still 2GB usable.
  3. ^ I agree unless you already own the 760s. Also the GTX 780 is getting a refresh as the 780 Ghz Edition and those should be available in a week or 2. A new stepping means higher clock speed.
  4. photonboy said:


    One reason I may have to go the 760 route is simply room. The 780 is an entire inch longer than the 60's. I'll be measuring tonight to see what the verdict is, but thanks for the very detailed explanation.
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