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GTX 970 in PCIe 3.0 x8 slot?

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Erisa
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Wednesday, April 13, 2016 3:45 PM (permalink)
I just built a new rig with the ASUS ROG Maximus VIII Gene MB and Noctua NH-D15S cooler.  Unfortunately, the cooler, while powerful and quiet, overhangs the first PCIe slot, which is the x16/x8 one.  If I install my EVGA GTX 970 in the second PCIe 3.0 x8 slot, will the lack of the full x16 hurt my graphics performance?  Are there issues with using the second slot?  I know that the recommendation is to put it in the first.
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    BrandonS
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    Re: GTX 970 in PCIe 3.0 x8 slot? Wednesday, April 13, 2016 3:53 PM (permalink)
    Even on a 980 Ti the difference is less than 1FPS; X8 doesn't hurt your performance at all. 
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    bsmegreg
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    Re: GTX 970 in PCIe 3.0 x8 slot? Wednesday, April 13, 2016 4:16 PM (permalink)
    The diffrience between PCIe x16 and PCIe x8 is bandwidth. PCI lanes go to the CPU and each carry about 1GB/s so x8 carries about 8GB/s on PCI 3.0 which is more than the GPU needs. So you don't really need PCIe x16 with today's GPU's, but we have 16 PCI lanes for SLI because if you use SLI then the lanes are split between the cards so you have x8 on each card.

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    arestavo
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    Re: GTX 970 in PCIe 3.0 x8 slot? Wednesday, April 13, 2016 5:43 PM (permalink)
    On my X79 Dark and a 1650 V2 (4930K equivalent) I tested PCIE 3.0 X8 vs X16 with my overclocked 980 Ti (1454MHz), and in the Uniengine Valley benchmark there was a difference of 3 FPS favoring X16.

    That was a controlled benchmark, so when gaming the difference is negligable.
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    DeathAngel74
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    Re: GTX 970 in PCIe 3.0 x8 slot? Wednesday, April 13, 2016 6:58 PM (permalink)
    Pcie 3 x16 vs pcie 3 x8 is little to no difference. Even in the x16 slot my 970 ran at 8gb/s. The only time it really matters like bsmegreg stated is sli. Two 970s running a 8gb/s a piece is fine with me, I never saw a single 970 run higher bandwidth than 8gb/s anyway. Even in the x16 slot

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    Dschijn
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    Re: GTX 970 in PCIe 3.0 x8 slot? Wednesday, April 13, 2016 7:21 PM (permalink)
    Here is a very good article about GPUs scaling with PCIe bandwidth:
    http://www.techpowerup.co...Express_Scaling/7.html
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