The video out is fixed at 60hz so, at constant framerate, you can only output every frame, every two frames, every three frames etc. In other words you framerate is a factor of 60. You could tripple buffer and do variable rate so an average could be something like 40, but it would cost you 8M and variable framerate is perceived worse than constant. If you cannot hit 60 you better spend more time on getting game prettier at 30 than waste memory on a tripple buffer and get a stuttering game as a result. On current gen memory is not as much an issue but the variable framerate is still not perceived well.