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  1. #1
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    Maximus VI Formula no 16x PCIe?

    Hey everyone, can anyone help me figure out why I only get 8x speed with my 7950 (Direct CUII)

    Am I reading things wrong, I understand that with more than one PCIe slot populated that the lanes are split, however if I have just one card in the middle slot, should it not be x16?

    I don't want the card in the top slot for aesthetic reasons but as the board is labelled as 3 x 16x PCIe slots, should they not run at 16x whether my GPU is in the top middle or bottom?

    Thanks for any input to help me clear this up, either I'm confused or there is a BIOS setting that I need to change?

    Thanks

  2. #2
    ROG Guru: Yellow Belt Array CSN7's Avatar
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    only the first slot is wired with 16 lanes

  3. #3
    ROG Guru: Grand Master Array HiVizMan's Avatar
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    OP how do you know it is not running at 16x could you open CPUz and press that little question mark half way up and run that app to power your card up fully.
    To help us help you - please provide as much information about your system and the problem as possible.

  4. #4
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    Ah lame, how come they are called PCIe 3.0 16x slots in the manuals and spec sheets etc?
    From the Asus site "3 x PCIe 3.0/2.0 x16" is there no way to enable 16x on the middle slot? Intel need to sort that out, my crosshair IV formula allowed it nearly 4 years ago!

  5. #5
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    Quote Originally Posted by HiVizMan View Post
    OP how do you know it is not running at 16x could you open CPUz and press that little question mark half way up and run that app to power your card up fully.
    Yep, tried that, all it does is goes from idling at PCIe Version 1.1 to 3.0 but stays at 8x

    Bios also reports 8x and obviously states "not present" for the other two.

  6. #6
    ROG Guru: Grand Master Array HiVizMan's Avatar
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    The lane itself is 16x but as you correctly state the processor manages the PCIe controller these days. I will pull out a system and see if I can find some work around.
    To help us help you - please provide as much information about your system and the problem as possible.

  7. #7
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    Apart from the HD7950 populating the middle PCIe lane, are the other two PCIe lanes empty?

  8. #8
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    Quote Originally Posted by Bash4Sure View Post
    only the first slot is wired with 16 lanes
    Bash4Sure is correct, and there is no workaround. Take a close look at the middle and bottom slots: their electrical pins are populated only to x8. If you want x16, you must use the top slot.

    ETA: Can be seen in this photo (click it for the full-size version): http://www.ocaholic.ch/modules/xcgal....php?pid=43492
    Last edited by dingo99; 10-06-2013 at 06:18 AM.

  9. #9
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    Thanks for everyone's replies, I guess the picture below sums it up! I'm frustrated though as in all descriptions, they are referred to as 16x slots, the question is now, how much of an effect will it have on a) A heavily overclocked 7950 Direct CU II and b) A R9 290x in a few weeks? Is even the 7950 enough to saturate the lanes?

    I see only 50% GPU usage then I play Arma 3 using my 4770k @ a very stable 4.7GHz (65*C full load) Could this be a problem causing the deficit?

    If I have time, I may swap the card over later and get back with some results. Thanks again, James




    Click image for larger version. 

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  10. #10
    ROG Guru: Grand Master Array HiVizMan's Avatar
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    This last question I can answer quite easily. NONE at ALL

    LOL yes that is true, even if you were to OC your vga with LN2 you will not max out the PCIe 8x lane with that video card.
    To help us help you - please provide as much information about your system and the problem as possible.

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