Putting 670s in SLI kills performance.

I recently picked up the GTX670 FTW by EVGA to go with my GTX670 Direct CU 2 TOP from Asus and i wanted to SLI them.

This went fine, but now when the cards are in SLI, the performance drastically goes down and things which should be smooth, becomes incredibly choppy and stuttery..

I have tried them both out of SLI and there are no problems at all. They both run perfectly fine under the same conditions with no issues whatsoever.

I have run out of ideas as to what is causing this. Ive done a full reformat, reinstalled the drivers, even tried using a different SLI bridge. nothing has worked.

I can still return the EVGA 670 for a full refund, but i know the card itself is not at fault and i want to keep it, but not if this continues.

Here is my computer specs:

Intel i7 3820 LGA 2011.
Asus P9X79 Pro motherboard.
Corsair Vengeance DDR3 RAM, 16GB.
Asus GTX670 Direct CU 2 TOP
Corsair ATX1200W PSU.

If anyone has an idea as to what is going on here, i would greatly appreciate your feedback on this.

Thanks much.
5 answers Last reply
More about putting 670s kills performance
  1. Can anyone help on this? Surely there's a fix out there. It cant be the board as I used to run GTX560 Ti's in SLI and never had these problems...
  2. Is this a problem with all games, or only 1 game? If so, what game?
    Do both cards work good when in the system alone?
    What does GPU-Z show in the bus interface?

    If the 560's have no issue, could the PSU be bad and not have enough power for your 670's?
    What drivers are you using? Did you install new ones for the 670's or using the old 560 ti drivers?
  3. This happens with all games. Both cards on their own run all games flawlessly. When they are in SLI, the framerate stutters and sometimes the whole screen will lock up for a second or 2. Just recently while playing Starcraft 2, the whole screen went black for about 7 seconds and then came back, with my fps at about half what it usually is.

    Both cards are great when they are running on their own. Only SLI is causing this.

    GPU-Z shows the EVGA card running at PCI-e 3.0 consistently. the Asus card dips to 1.1 on a regular basis, in or out of games.

    I doubt its the PSU. its a 1200w Corsair and shouldn't have any trouble with 2 670s.

    Drivers are the latest from Nvidia for the 670. I'm not using the beta drivers.

    I recently updated my motherboard's BIOS to see if that would work, and it didnt.
  4. What PCIe slots are you using? You should be using the blue slots to give lots of space between cards, and to insure you are in x16/x16. You may also want to try 1 card in both slots on their own, to insure the PCIe Slot is working properly.
  5. I am using the 2 blue slots on the motherboard. I just switched the cards to see if that will make a difference. GPU-Z now reports the EVGA card, now in the bottom port, is fluctuating between PCI-e 2.0 and 1.1.

    The Asus card started life in the top blue slot, and i moved it down to the bottom one after I anticipated getting another 670 to go with it.

    The Asus card ran great in both ports before i got the EVGA 670, so that is one problem ruled out.
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