If I dump the GPU in the second PCI-E 16x socket; it goes to hell. It stutters, lags, sometimes completely locks up. I'm really not sure what's doing what at the moment. Edit; OKay. 280 drivers are still crashing if I enable SLI, (Blue-screen while the GPUs were busy messing around, didn't get to see the cause. Probably that damn NV.sys file, though.) Lets go back to the stoneage; 275.50 beta. The very first drivers to support SLI on my motherboard.