Depends. PC gaming isn't like console gaming where there is a standardized set of hardware and developers can 'target' a specific framerate for the game to run at and adjusting textures/level of complexity to suit. In PC gaming, where there is no standardized set of hardware, I think developers usually aim for specific levels of detail and just let the hardware run it as well as it can. So it depends on the CPU-dependence and GPU-dependence of the specific game.