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ASRock 970 Extreme4 Crossfire (PCIe x16, x8, x4?!)

Hello,

I was looking at the ASRock 970 Extreme4's specs lately and found them very confusing.
It supports dual/tri/quad Crossfire and dual SLI but when it comes to the whole PCIe x16/x8/x4 stuff it gets weird.

It says this:
- 3 x PCI Express 2.0 x16 slots (PCIE2/PCIE4: single at x16 (PCIE2) / x8 (PCIE4), or dual at x8 (PCIE2) / x8 (PCIE4) ; PCIE5: x4 mode)

Can someone translate what this means. In dual crossfire is it 2 x x16 or 2x x8 or x16 and x4?

http://www.asrock.com/mb/overview.asp?cat=Specifications&Model=970%20Extreme4
http://www.asrock.com/mb/compare.asp?SelectedModel=Z87+Extreme4&SelectedModel=Z87+Extreme3&SelectedModel=990FX+Extreme4&SelectedModel=990FX+Extreme3&SelectedModel=970+Extreme4
9 answers Last reply Best Answer
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  1. Best answer
    Only first slot works at full speed. Other slots are x16 slots but work at lower speed. 2nd slot is x8 and the third is x4. If use crossfire or sli or just stick in two PCIE x16 cards in first ad slot, then both the cards will work at x8 speed. Here first and second slot share the bandwidth. In a simpler way if you are planning to use two powerful GPU cards then your cards will be bottlenecked.
  2. If you have one card it works at:
    x16 in slot marked as PCIE2 or x8 when in PCIE4 slot

    With two cards, each works at
    x8 with cards in slots PCIE2 and PCIE4 (SLI supported)

    PCIE5 operates at x4 at all times.
  3. Xttony said:
    In a simpler way if you are planning to use two powerful GPU cards then your cards will be bottlenecked.


    From the benchmarks I've seen the loss is negligible but they are pretty old. Don't suppose you know of any more recent x8/x8 benchmarks?
  4. Performance drop is negligible but don't take any chance. Anyway verify that the benchmarks you checked used PCIE 2 slots and not PCIE 3 slots. For example two R9 290x cards will be bottlenecked
  5. They are PCIe 2.0 but they're two years old. Have gpus progressed to such a stage that you'd see a significant difference?
  6. Can u give a link to that benchmark? If the benchmark is using GTX 600 and AMD HD 7000 series cards then no cards haven't progressed a lot
  7. Xttony said:
    Can u give a link to that benchmark? If the benchmark is using GTX 600 and AMD HD 7000 series cards then no cards haven't progressed a lot


    Ok, just found a newer one. Seems to be a matter of a couple of % at 1080p

    http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/19.html
  8. We'll they don't differ by much but we don't really know if they are using any mods at all. Anway I don't think you'll have much problem adding 2 cards to your system. If you are using 2 cards the memory will be shared anyway so about half the load.
  9. Anyway if you are not going above 1080p resolution you won't have any problems
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