You'll be able to run your games, but you won't be able to run any of the Nvidia specific features. Of course GPU PhysX will no longer be an option (weapon debris effects in Fallout 4, for example). But then also several antialiasing options (MFAA, TXAA, FXAA, TrSSA), anisotropic filtering options (HBAO+, which can be forced on in many games that don't support it, Skyrim was a notable example), and VSync options (Adaptive VSync, Fast Sync).