SLI problems on AM3+

I hope to find people who have solved this problem. I run SLI GTX 570s. I was running that on my faithful old ASUS M4A79 Deluxe AM3 (DDR2) motherboard using a Phenom II X6 1100t CPU. Of course this was sub-optimal because the board is DDR2 and SATA2 and didn't offer official SLI support. I noticed that my GPU utilization was low rendering any scene with any kind of geometry on it.

So I figured, it's either the modded drivers that are giving me "sli support" but not quite right, or the DDR2 that's starving my 6 cores and my SLI subsystem. So I bought me a brand spanking new MSI 990FXA-GD80 mobo with DDR3, SATA3, and official SLI certification, thinking it would solve my problem.


I am still saddled with a GPU utilization that tends towards 50% when scenes have a lot of stuff on them, in most games (Skyrim and BF3 are two prime examples). So basically what I am seeing is the performance of a single GTX 570 most of the time, and the performance of SLI when I least need it.

Someone told me my PSU might be underpowered but I don't see that as possibly causing this stuff, given that the cards ARE able to run at 95%+ at times (Metro 2033 is one example).

What it looks like is some weird PCI-E choking mechanism that basically limits my total PCI-E bandwidth to what one card can use, so when the scenes are simple the GPUs can work but whenever they get more complex the GPUs get data-starved and run at half load.

I have updated every driver and BIOS (even on the video cards). I have tried a fresh install of win7. I benchmarked my system with each of my GTX 570s separately and the scores are practically identical. I could not see the GPU load during my runs with 3D Mark 2011 basic because the MSI Afterburner wouldn't show. So anyway, that rules out one of the cards being somewhat defective. I thoroughly dusted my air filters and even opened up my case. The problem still persists.

So, does anyone have ideas what would be my next step? I am seriously considering moving over to an Intel CPU but if there is any way to stick with what I have, well that's what I want to do. Hell, it seems no one can guarantee me the problem will be gone if I go and spend another $600 to rebuild on Intel...

Cpu: AMD Phenom II X6 1100t @ stock 3.3 Ghz + Noctua NH-D14
Ram: Corsair 2x4gb DDR3 1866
Mobo: MSI 990FXA-GD80 (replaces an ASUS M4A79 Deluxe)
HDD: Crucial M4 128gb SSD + WD Caviar black 1tb + 1.5tb
PSU: Corsair TX850W
Sound: Auzentech Prelude X-Fi + Sennheiser PC 360 G4ME headset
Graphics: SLI MSI GTX 570 OC Edition
Input: G-15 keyboard + Logitech G5 gaming mouse
Monitor: Samsung 2233rz 3D ready 120hz + nVidia 3D Vision + Acer 17" secondary monitor
OS: Windows 7 64 Ultimate
Case: Antec Twelve Hundred
7 answers Last reply
More about problems
  1. Hve you checked your Nvidia control lately? Enable 3D?
  2. I check it all the time, and sometimes I enable 3D and sometimes disable it... What of it?
  3. Just to check...
    Did you put the SLI bridge?
    Did you activated SLI inside Nvidia drivers?
  4. BTW
    Your PSU can run these SLI without a problem!

    Just to test these board PCI lanes.
    Remove your auzentech x-fi.
    And try to run again your games. See if these soundcard is stealing lanes from VGA or not.
  5. Your system should be 'Smokin' with that setup. Try unplugging the lower res monitor.
  6. SLI is activated. The SLI bridge is connected onto the connectors closest to the backplate.

    I unplugged the secondary monitor and removed my sound card. BF3 seems to play somewhat better, with GPU utilization hovering aroung 60% and CPU still not close to being fully utilized. I will try 3DMark 2011 and see if that is improved.

    EDIT: No improvement in 3D Mark 2011 to report.
  7. Any ideas at all guys?

    I'm about to press the button and risk $600 to MAYBE fix my problem... :-/
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