For games and graphics? I don't think so, a GPU has a ton of dedicated hardware that is very costly to simulate in software: triangle setup, rasterizers, tessellation units, texture mapping units, ROPs... and now even raytracing units.
For games and graphics? I don't think so, a GPU has a ton of dedicated hardware that is very costly to simulate in software: triangle setup, rasterizers, tessellation units, texture mapping units, ROPs... and now even raytracing units.