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How important is it to have two PCIe x16 3.0 for SLI ?

Discussion in 'Video Cards & Monitors' started by Embercide, Aug 19, 2015.

  1. Embercide

    Embercide Member

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    I'm in the process of purchasing hardware for my Skylake upgrade so that i'm ready when Vive/Oculus goes on sale.
    I've decided on a single 980ti to start with, with the intention of getting a 2nd for SLI in the next few years if required.

    Which leads to my question.. Just how important is it for performance to get a motherboard that has two full PCIe x16 3.0 slots? When the day comes that I run two of these in SLI (and that day may never come!) will I be kicking myself if the motherboard only does two x8 3.0 slots?

    Every motherboard under $700 will do one full x16 3.0, or two x8 3.0
    One motherboard @ $800 does two x16 3.0
     
  2. Scarecow

    Scarecow Member

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    it makes zero difference if your running at PCIE 3 x8 or x16, even using PCIe 2.0 x8 there is no noticeable performance increase or decrease so dont spend $800 on a motherboard just for that
     
  3. OP
    OP
    Embercide

    Embercide Member

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    Even though that particular card specs say it can use 3.0 and x16 :confused:
     
  4. Scarecow

    Scarecow Member

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    yup but that dosnt mean its only PCIE 3.0 x16, thats the max it can run at, you will see no difference from running the card at x16 or x8
     
  5. Paulie_AU

    Paulie_AU Member

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    You dont need it nothing can saturate the bandwidth of 3.0 x 8
     
  6. Dangerous1

    Dangerous1 Member

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    No real world difference between x8 and x16. I've looked at a lot of gaming benchmarks and there is no difference.
     
  7. walker_2003

    walker_2003 Member

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    insane diff..

    [​IMG]
     
  8. Newbie12

    Newbie12 Member

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    A very tiny difference(in today's world), but get it so you can future proof yourself when graphics cards actually need full 16 lanes of gen 3 PCIE buses when SLi'ing or CrossFire'ing.:thumbup:
     
  9. James086

    James086 Member

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    It only becomes a problem at high resoultions (like 4K) when you have a lot of bandwidth going between cards due to the higher resolution. I assume it will be fine based on PCIe 2.0 x8 x8 being enough for me when I was running 5760*1080 which is 3/4 of the resolution of 4K.
     
  10. Frag

    Frag Member

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    As other have said the really high bandwidth resolutions may have more of an impact but we are still talking a couple % at most.

    I went from 2x 16 PICE 3.0 to 16/8 as my sound card took up too much room on the mobo. 0 difference, I mean zero - this was only 1440p.

    This may be a little different with DX12, so I will revisit it then but I doubt it will have any impact.
     
  11. mshagg

    mshagg Politburo

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    The only scenario I can think of is using AMD cards in CFX at very high resolutions and very high framerates, given all of that data is passed between the cards via pcie, in addition to the drawcalls from the cards.
     
  12. munchkin1

    munchkin1 Member

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    I've been running x8/x8 for a few years now on a Z77 mobo with 2xGTX770. Am yet to see any reason to try get x16. Significant extra cost for minuscule performance gain...

    IMO if you're the type to buy SLI, then you're also the likely the type to keep your PC relatively up to date, so future proofing this is silly, by the time it's needed you'll be upgrading anyway, at least that's what I figured for myself.

    If you have the money though then by all means go for it, if it was only a small cost difference I know I would just because :p
     

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