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PCI 16x running at 8x

Hello,

In my thread here:

http://www.tomshardware.com/forum/278226-33-video-card-slot

I inquired about using a GPU in the 2nd PCI-E slot, but only s single GPU. I have installed it as such and it is running at 8x.... Even though there is only one card. Is there any way to force the bios to run this at 16x, or is this slot simply limited to 8x? This is something I tried to resolve before buying the board.

Thanks!
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  1. Best answer
    sgt bombulous said:
    Hello,

    In my thread here:

    http://www.tomshardware.com/forum/278226-33-video-card-slot

    I inquired about using a GPU in the 2nd PCI-E slot, but only s single GPU. I have installed it as such and it is running at 8x.... Even though there is only one card. Is there any way to force the bios to run this at 16x, or is this slot simply limited to 8x? This is something I tried to resolve before buying the board.

    Thanks!


    The CPU has 16 lanes. Eight of them go directly to the top slot. Eight of them go to electronic switches.

    Those switches are connected to the first and second slot. When you add a card to the second slot, it gets those eight lanes. When you remove the card from the second slot, the top slot gets those eight lanes in addition to the eight that are always connected.

    So your options are x16/x0 or x8/x8 where the second slot is after the / mark.
  2. Crashman said:
    The CPU has 16 lanes. Eight of them go directly to the top slot. Eight of them go to electronic switches.

    Those switches are connected to the first and second slot. When you add a card to the second slot, it gets those eight lanes. When you remove the card from the second slot, the top slot gets those eight lanes in addition to the eight that are always connected.

    So your options are x16/x0 or x8/x8 where the second slot is after the / mark.


    I guess you can never be too precise when phrasing a question... Your information seems to reflect what's happening. This is also one of the reasons I avoided an eVGA mobo because the 2nd PCI-E slot specifically said "x8" on it... Turns out they were just being honest. So would I expect to take a performance hit running it there? I have a GTX260.
  3. sgt bombulous said:
    I guess you can never be too precise when phrasing a question... Your information seems to reflect what's happening. This is also one of the reasons I avoided an eVGA mobo because the 2nd PCI-E slot specifically said "x8" on it... Turns out they were just being honest. So would I expect to take a performance hit running it there? I have a GTX260.


    The EVGA board is a great part, did you even bother reading the motherboard roundups? There's a list of slot functions on Page 2:

    http://www.tomshardware.com/reviews/lga-1156-motherboard,2463.html
    http://www.tomshardware.com/reviews/enthusiast-p55-motherboard,2494.html

    Anyway, I wouldn't expect to notice the performance difference with a GTX260. Check out the scaling analysis article:

    http://www.tomshardware.com/reviews/p55-pci-express-scaling,2517.html
  4. Crashman said:
    The EVGA board is a great part, did you even bother reading the motherboard roundups? There's a list of slot functions on Page 2:

    http://www.tomshardware.com/reviews/lga-1156-motherboard,2463.html
    http://www.tomshardware.com/reviews/enthusiast-p55-motherboard,2494.html

    Anyway, I wouldn't expect to notice the performance difference with a GTX260. Check out the scaling analysis article:

    http://www.tomshardware.com/reviews/p55-pci-express-scaling,2517.html


    The eVGA doesn't have IDE connections, I didn't feel like replacing both optical drives - right now. I can always replace them later. Ratings for the EVGA in this price range and the ASUS I bought were similar anyway. Thank you for getting back to me.
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