GPU utilization drops to 50%, CPU usage not maxed - ???

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I'm using a Core 2 Duo 6750 at stock speeds with two 9600GT in SLI. Playing Fear 3 I normally get around 80fps, with both GPUs pumping along at 98% or so use, and it's good. But them sometimes for a few seconds both of them will drop to 50% utilization and I'll end up around 40 fps. That's still playable, but I think something has to be up for that to happen. It doesn't drop to "around" 50%, it drops to exactly 50% on both GPUs.

I recently beefed my PSU up to 850W in anticipation of a future build, so I know it can't be lack of juice. Any ideas? I think I'll try it with one GPU and see if I get similar drops.

Edit: With SLI set to single GPU I do not get drops to 50% utilization. I get around 45fps. What could be causing it to sometimes drop to single GPU performance? Is it just a SLI quirk?

 

[smorizio]

I'm using a Core 2 Duo 6750 at stock speeds with two 9600GT in SLI. Playing Fear 3 I normally get around 80fps, with both GPUs pumping along at 98% or so use, and it's good. But them sometimes for a few seconds both of them will drop to 50% utilization and I'll end up around 40 fps. That's still playable, but I think something has to be up for that to happen. It doesn't drop to "around" 50%, it drops to exactly 50% on both GPUs.

I recently beefed my PSU up to 850W in anticipation of a future build, so I know it can't be lack of juice. Any ideas? I think I'll try it with one GPU and see if I get similar drops.

Edit: With SLI set to single GPU I do not get drops to 50% utilization. I get around 45fps. What could be causing it to sometimes drop to single GPU performance? Is it just a SLI quirk?

may be the cards bios or the driver seeing the cards get close to there max temps and try and throttle down the cards. i would use msi afterburner and see what the temps of the cards are when maxed and the fan profile. you may want to max the fan out sooner and check that both cards gpu fans are working fine.