2 660Ti's running SLI worse than one 660Ti

Discussion in 'Videocards - NVIDIA GeForce' started by Davor7, Oct 30, 2012.

  1. Davor7

    Davor7 New Member

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    GPU:
    (2)Gigabyte 660Ti 2GB
    Not sure what the problem is. I had 2 GTX480 SLI go bad on me. Replaced them with 2 660Ti's and running them SLI. For some reason, if I run them SLI, the performance drops like a rock. I thought maybe the drivers so I reinstalled them and that didn't work. Then I installed the newer beta ones (310) and still loss of performance. Ran Windows Performance index (just to see if there is a difference) and sure enough, running in SLI and the graphics got a score of 6.7. If I turn SLI off, then I get 7.9.

    Even though I am running Windows 8 Pro now, this was happening on Windows 7 Ultimate. Both 64-bit.

    Both cards work great solo but in SLI, its like they die.
     
  2. scheherazade

    scheherazade Ancient Guru

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    Make sure that one of them isn't on a lower-speed pci-express connection.

    I've had SLI issues when one card is on an x16, and the other on an x4.

    -scheherazade
     
  3. Davor7

    Davor7 New Member

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    If you're the meaning slots, the cards are in the same slots as the old ones. Should be running both at x16. Does it matter which connection I bridge the 2 cards (i.e. the cards have 2 bridge connect, side by side on the card). I wonder if the MB itself is going bad?
     
  4. aless83

    aless83 Master Guru

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    post you MB specs, it's probably the PCIX x4 problem
     

  5. Davor7

    Davor7 New Member

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    GPU:
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    http://www.newegg.com/Product/Product.aspx?Item=N82E16813131614

    I did look in the BIOS and make sure it was set to x8/x8 (I was wrong on the x16/x16 part). Anyways, I manually set the PCIe to x8/x8 in the BIOS. Still big drop in performance. So its either the SLI bridge that connects the cards together or the MB itself that is maybe going bad.
     
  6. lehtv

    lehtv Ancient Guru

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    Try doing some real tests.
     
  7. airbud7

    airbud7 Ancient Guru

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    [​IMG]

    Looks like they use the first set...
     
  8. Sever

    Sever Ancient Guru

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    what clock speed is your CPU running at? SLI normally requires more cpu power as well.
     
  9. Davor7

    Davor7 New Member

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    Yea found that too airbud7. Thanks though. I did use the "correct" ones.





    I had it at stock, 2.8Ghz and its a i7 930. I know that isn't the problem as my last cards, GTX480's running SLI, had no problems. But I did over clock the CPU to 3.8Ghz and changed the DRAM to 1482 to see if the CPU speed was the problem. CPU test and memory test showed the OC was great but the SLI was still problematic. Also, games would crash with SLI running with the new 660Ti's running or freeze up, black screen for 5 seconds then back to the game. But got the display drivers have been recovered message.
     
  10. Shadowdane

    Shadowdane Maha Guru

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    Maybe one card is faulty?? Try the cards separately and see if one is troublesome?
    When I first installed my GTX680s, I had one bad card. I wasn't see slow performance but was getting constant freezes and lockups. I tested them individually and found one card to be causing the problems.
     

  11. Davor7

    Davor7 New Member

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    I was going to post that I did. Forgot. Yes I tested them solo, each one by itself and both work great.
     
  12. eagled1

    eagled1 Master Guru

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    Make certain you are sure that the SLI bridge is good. Had this happen to me once. Make sure you have removed all driver remnants and clean installed the newest driver.
     
  13. Fox2232

    Fox2232 Ancient Guru

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    Long Time ago I saw test for PCIe 2.0 SLI 16x+16x versus 4x+4x. And difference was between 1% to 5% based on game/bench used. (tested with 2x GTX 480 = similar demands like your cards)

    You are not playing Windows Experience Index, you are playing games. Do little Bench with GPU dependent games like AvP 2010.

    You may be running into unfortunate negative SLI scaling issue. 4xx series are quite different to 6xx series.

    What games you tried? And what results you got? You may find that other people had same results at that game like you. Multi card configs were always bit risky. Matching driver to game where it is best.
     
  14. Davor7

    Davor7 New Member

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    Sorry for the long no response. I went ahead and placed my motherboard to this: http://www.newegg.com/Product/Product.aspx?Item=N82E16813131658

    My rig now has a i7-930 @3.6GHz
    That MB I linked
    12GB DDR3 @1435Ghz
    2 Gigibyte 660Ti with SLI off for now
    90 and 240 GB SSD drives
    and this PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E16817121037
    And a Samsung SyncMaster 2443 24" LCD

    So with the system I have and if I play games like SWTOR and Rift, SLI really is worse because of CPU bottleneck from the SLI overhead as those games are more CPU intensive, correct? If I was playing games like BF3 or Metro, I would see better performance or are these 660Ti's in SLI too much for this rig and just better to sell the 2 cards and get one 680?
     
  15. Davor7

    Davor7 New Member

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    UPDATE:

    Ok, after reinstalling windows (because of the new motherboard), I decided to test out using 3D Mark 11 with SLI and without SLI running. It looks like CPU bottle-necking is happening with games that are more CPU intensive (MMO's, RTS's) than with games that are more GPU intensive (FPS's). Well, I decided to just keep those cards and I can turn on or off the SLI for games I want to use it for and others I don't.

    After running 3d Mark 11, without SLI, the average FPS was about 30 to 45. With SLI running, 75 to 95 FPS. No problems at all and FPS was definitely much better with more GPU type test. Guess I am still pretty new with SLI and what games use it better. And, future-proofing the old computer for a while. Games might start using SLI more and I will be good to go for them. :)

    Still open for any thoughts or suggestions in this thread if anyone has any! Thank you to those helped me on this!
     

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