The default, 3. Taken from TweakGuides NVIDIA driver article: "Maximum Pre-Rendered Frames: If available, this option - previously known as 'Max Frames to Render Ahead' - controls the number of frames the CPU prepares in advanced of being rendered by the GPU. The default value is 3 - higher values tend to result in smoother but more laggy gameplay, while lower values can help reduce mouse and keyboard lag. However extremely low values such as 0 may hurt performance, so I recommend this option be kept at its default of 3 globally, and only adjusted downwards in specific game profiles. Remember, in most cases mouse lag is due to low framerates, so adjusting this option is not an automatic cure to lag issues, nor should it be the first thing you try. Finally, it only works in DirectX games, not OpenGL games." Personally, I've never had any reason to alter this value as I don't believe lowering or raising it has any beneficial impact on games overall.