SLI performance significantly worse than single card

Problem: My framerate in games with SLI enabled is at best the same as with a single card, and at worst 80% slower. For example, the Metro 2033 menu screen in sli runs at 4-5fps and takes 40s for the textures to even load, vs 25fps with a single card. This is just in the menu screen. Something is not right here.

Background: I've had SLI working fine for a few months and I know how to work profiles, so I don't think that's it. The drivers are the latest WHQL certified drivers and they worked fine for a while. I tried nvidia recommended settings, I tried force alternating frames, etc. Nothing I've tried has worked so I'm beginning to think there might be a hardware issue somewhere. Thinking it was a video card issue, I ran a single card in each pci-e port and stressed it for a while. Both cards checked out fine in single configuration, so I swapped their pci-e ports and ran sli again. Same abysmal SLI performance.

I recently moved and haven't done any gaming for the last few weeks. I've had power issues with this apartment (dimming lights, etc), but nothing more than that. Just a few days ago my pc started randomly rebooting, so I swapped the power supply and things seem to be ok (so far), except for the framerate issues. Is there any way to tell if the motherboard or gfx cards were damaged in some way? Like I said, both cards checked out fine in single configuration. I'm stumped.

System Info:

OS: Windows 7 Professional 64-bit
CPU: i5 2500k running at stock
Mobo: MSI P67A-GD65 (B3). Drivers up-to-date.
RAM: 8gb G.Skill Ripjaws DDR3 1600
GPU: MSI GTX560 Ti twin frozr II/OC x 2 (in SLI). nVidia drivers: 280.26 (most recent WHQL)
PSU: Corsair TX750
HD: WD 1TB caviar black as main, then two small archive HDs
DVD: generic DVD
4 answers Last reply
More about performance significantly worse single card
  1. Seems basic, but did you do a complete driver uninstall AND wipe (with Driver Sweeper) before installing the latest drivers with SLI?
  2. Yeah, I did that. Then redid that. No change.
  3. I had a Similar Problem with my GTX275's. After some Troubleshooting and Popping/Swapping, I was able to determine that one of the Video cards had a Problem with it. Only thing is, it was not noticable when not gaming. Anytime I tried to open a game it would deteriorate. I do not know how Savy you are when it comes to cracking the case, but I would try and see if you could determine which card might be causing the problem. My cards were almost 2 years old, and EVGA still RMA'd the bad card. got the new card within a few days problem fixed. I would try that as your next step. I do not know much about MSi, but I think EVGA had a 5 year warranty on all their cards. Good Luck!!
  4. Well, I think I've narrowed it down to two independent problems that I thought were related. I swapped out my psu with an older one and the random reboots have stopped. The other problem seems to be primarily with Metro 2033. I haven't played many games in the last few months, but decided to try the $5 Metro steam deal. I can seem to get SLI working with all of my other games now, but the SLI performance gain in Metro is inverse. I ran the Metro benchmark just to see what would happen and I averaged 4.75fps in 1920x1200, medium settings. Here's the kicker; I get roughly the same framerate whether at high or low settings. I suspect I'm missing something and haven't been able to figure it out. I'm not too worried about being able to play Metro, but rather that my system is doing what it's supposed to...which it's not.
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