XNA 4.0 runs at 50 instead of 60 fps - xna

Question

I'm experimenting a bit with XNA 4.0, following tutorials and creating very basic stuff (like a triangle and some lines ;-)). While doing this, I noticed that all my applications never run at more than 50-51 fps (with Fraps). It's not that I'm running heavy programs on a slow computer or graphics card (Ati HD4870), it must have something to do with XNA (games run just fine here).
Now, everything I read about XNA says that the default update frequency is 60 times a second, and I'd like to get that.
It's the same in full screen as in windowed
If I set SynchronizeWithVerticalRetrace to false or true: same
If run the program without Visual Studio, I only get 41 fps
When I override the update frequency by using TargetElapsedTime = new TimeSpan(0, 0, 0, 0, 10); the fps does go up significantly. I noticed though that this still isn't correct: the 10 means 10ms, yet I 'only' get 83 fps instead of 100. At 1ms I get 850 fps. So the deviation of what fps I get and what I should get is pretty consistent. It looks to me like there's just something wrong with the timing?
Anyone knows what might be the problem here and/or has suggestions to get a stable 60 fps?
Thanks!

Answer 1

Isn't it possible that FRAPS isn't giving you accurate results? Have you tried adding in your own framerate counter to the game and seeing what those results say? Shawn Hargreaves has a method he coded up on his blog that should be pretty painless to add to a new blank XNA game project.
http://blogs.msdn.com/b/shawnhar/archive/2007/06/08/displaying-the-framerate.aspx
Do you see the same FPS or is reported differently when you do the calculation yourself?

Answer 2

I put together the following code on XNA 4 and it's getting a locked 60 fps. Try it out on your system (You'll just have to add the appropriate sprite font) and see if you get 60 fps too. If so, put the adjustments in your problem code and see if you get the same result.
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
namespace _60fps
{
public class Game1 : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
SpriteFont OutputFont;
float Fps = 0f;
private const int NumberSamples = 50; //Update fps timer based on this number of samples
int[] Samples = new int[NumberSamples];
int CurrentSample = 0;
int TicksAggregate = 0;
int SecondSinceStart = 0;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
}
protected override void Initialize()
{
base.Initialize();
graphics.SynchronizeWithVerticalRetrace = false;
int DesiredFrameRate = 60;
TargetElapsedTime = new TimeSpan(TimeSpan.TicksPerSecond / DesiredFrameRate);
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
OutputFont = Content.Load<SpriteFont>("MessageFont");
}
protected override void UnloadContent()
{/* Nothing to do */}
protected override void Update(GameTime gameTime)
{
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState(PlayerIndex.One).IsKeyDown(Keys.Escape))
this.Exit();
base.Update(gameTime);
}
private float Sum(int[] Samples)
{
float RetVal = 0f;
for (int i = 0; i < Samples.Length; i++)
{
RetVal += (float)Samples[i];
}
return RetVal;
}
private Color ClearColor = Color.FromNonPremultiplied(20, 20, 40, 255);
protected override void Draw(GameTime gameTime)
{
Samples[CurrentSample++] = (int)gameTime.ElapsedGameTime.Ticks;
TicksAggregate += (int)gameTime.ElapsedGameTime.Ticks;
if (TicksAggregate > TimeSpan.TicksPerSecond)
{
TicksAggregate -= (int)TimeSpan.TicksPerSecond;
SecondSinceStart += 1;
}
if (CurrentSample == NumberSamples) //We are past the end of the array since the array is 0-based and NumberSamples is 1-based
{
float AverageFrameTime = Sum(Samples) / NumberSamples;
Fps = TimeSpan.TicksPerSecond / AverageFrameTime;
CurrentSample = 0;
}
GraphicsDevice.Clear(ClearColor);
spriteBatch.Begin();
if (Fps > 0)
{
spriteBatch.DrawString(OutputFont, string.Format("Current FPS: {0}\r\nTime since startup: {1}", Fps.ToString("000"), TimeSpan.FromSeconds(SecondSinceStart).ToString()), new Vector2(10,10), Color.White);
}
spriteBatch.End();
base.Draw(gameTime);
}
}
}