So i have been playing with this for a day or so. here are my findings and maybe i can get some help as to why SLI stinks on my rig. With fresh un-modded 310.70 drivers installed, obviously i am in single card mode. Quick benchmark with Furmark on all default settings yields me 45 FPS. Using single GPU obviously. Next i mod the drivers reboot and enable sli, run the benchmark again, this time i get a lowly 23 fpc, but both cards report their GPU cores as being taxed 90-98% So, after this i turn sli off, so essentially its running in single card mode. and i still get a lowly 23 fps in the Furmark benchmark, and uit shows it is only using 1 GPU according tot he core load stats in Furmark as well as open hardware monitor. I reinstall the driver unmodded and i am back to double performance in the benchmark, one card obviously as it is not Sli capable on the unmodded driver. All 3 tests above were run while both cards were installed in to the system, SLI bridge obviously installed as well. I find it odd that the onyl time the single card performs well si when there is no driver mod, using just a single card with sli off with the modded driver still bust up my performance. Specs: Mainboard: P5Q3 Ram: 6 GB 3x2GB OCZ Gold 667mhz CPU: Core 2 Quad Q6700 2.66GHz Videocard 1: EVGA GTX 460 SSC Videocard 2: EVGA GTS 450 Temperatures under full load are all very acceptable. and well with in the Specs of the manufacturer. No gpu or cpu throttling is detected on my part. No overclocks. PSU is a TR2-500W That i pulled apart and put in low ESR Panasonic caps, and a better higher amp bridge rectifier. Taxing the cpu and both gpu's running a combination of OCCT and fluid mark shows that all 4 cores and both gpu's are running at 100%, UPS reports that the total draw at full load is 398W fluttering to 422W. I am nto concerned about the psu, But i may replace it as a test if you all don't have other ideas. the funny thing is i can have fluid mark running pure Physix on the 450 GTS and max its gpu to 100% and fire up Furmark at the same time and still get about 38 FPS on the 460 GTX. So i don't suspect the PSU as i can load up both cards separately when the driver is un modded and have higher performance then both cards loaded up witrh the modded driver. Sorry its so long winded!