title: CADisplayLink running lower frame rate on iOS5.1
body: <p>I'm using <code>CADisplayLink</code> in my iPhone app. </p>
  
  <p>Here is the relevant code:</p>
  
  <pre><code>SMPTELink = [CADisplayLink displayLinkWithTarget:self selector:@selector(onTick)];
  SMPTELink.frameInterval = 2;//30fps 60/n = fps
  [SMPTELink addToRunLoop:[NSRunLoop mainRunLoop]
                      forMode:NSDefaultRunLoopMode];
  </code></pre>
  
  <p>onTick is thus called every frame of <code>30FPS</code> (1/30th of a second). This works GREAT on <code>iOS6</code>+ - does exactly what I need. However, when I ran my app on an iPhone 4s running iOS5.1, the onTick method ran slightly slower than with the iOS6 counterpart. Almost like it was running it <code>29FPS</code>. After a little bit, it was out of sync with the iOS6 iPhone 5. </p>
  
  <p>The code in the onTick method is not time consuming (that was one of my thoughts...), and it's not the iPhone because the app runs fine on an iPhone 4s running iOS6. </p>
  
  <p>Does <code>CADisplayLink</code> function differently in <code>iOS5.1</code>? Any possible workarounds/solutions?</p>