Poor performance/FPS

maerean_m · 02-02-08, 01:48 AM

VSync ON can hit FPS really hard.

Depending on what the game does at the moment, the updating gets done in X milliseconds and the rendering in Y milliseconds. The FPS you get is 1000/(X+Y).
If your FPS is 50, X+Y equals 20.

When VerticalSync is activated, the card won't start displaying the image until a new screen refresh starts. So when in 60Hz, on average, the render takes a 1000/60/2=8.3 milliseconds longer so your new FPS will be 1000/(X+Y+8.3).
Starting from 50 frames per second, you get 35 with VerticalSync.
That's on the average. In the worst case scenario, your FPS will drop to 27.

It's a big hit on FPS without any real visual improvements.

As seen from the formula, it helps a little if the refresh is set to 75Hz. The 8.3 milliseconds delay takes only 6.6 milliseconds and the FPS drops only to 38.

This low FPS can be the cause of your video card running in "2D" frequencies. The video card driver may say "this game is very CPU bound, instead of GPU bound, so the card will do great even with the 2D frequencies and the player will notice the reduced fan noise".

In Silent Hunter, switching the VerticalSync requires you to restart the executable (to reinitialize the Direct3D engine).

02-02-08, 01:48 AM	#15
maerean_m Captain Join Date: Mar 2007 Location: Bucharest, Romania Posts: 529 Downloads: 0 Uploads: 0	VSync ON can hit FPS really hard. Depending on what the game does at the moment, the updating gets done in X milliseconds and the rendering in Y milliseconds. The FPS you get is 1000/(X+Y). If your FPS is 50, X+Y equals 20. When VerticalSync is activated, the card won't start displaying the image until a new screen refresh starts. So when in 60Hz, on average, the render takes a 1000/60/2=8.3 milliseconds longer so your new FPS will be 1000/(X+Y+8.3). Starting from 50 frames per second, you get 35 with VerticalSync. That's on the average. In the worst case scenario, your FPS will drop to 27. It's a big hit on FPS without any real visual improvements. As seen from the formula, it helps a little if the refresh is set to 75Hz. The 8.3 milliseconds delay takes only 6.6 milliseconds and the FPS drops only to 38. This low FPS can be the cause of your video card running in "2D" frequencies. The video card driver may say "this game is very CPU bound, instead of GPU bound, so the card will do great even with the 2D frequencies and the player will notice the reduced fan noise". In Silent Hunter, switching the VerticalSync requires you to restart the executable (to reinitialize the Direct3D engine). __________________ Kilroy was here Last edited by maerean_m; 02-02-08 at 02:38 AM.