The performance penalty goes up as you apply AA and anisotropic filtering (AF). But overall, there’s still very little overhead seen in Left 4 Dead. And even with AA turned on, performance remains reasonable. In essence, the GTX is a cutting-edge card, so to have it cut to such meager frame rates is a shock. Fortunately, you can use two-way SLI to get your performance back up where it should be, if that makes sense. Whereas you might not have considered a second card for a jump from 100 to 175 FPS, in this case it might actually make good sense to jump from 45 FPS to something notably higher in a platform running a stereo setup.