title: SpriteKit performance drop when frame rate set to 60hz but NOT when 120hz on iPhone 13
body: <p>I've updated my SpriteKit game to iOS 15 and, when testing on an iPhone 13 Pro, I've discovered frame rate has steadily dropped to around 55-56fps on this device:</p>
  <p><a href="https://i.stack.imgur.com/TD0DC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TD0DC.png" alt="Can't make 60fps" /></a></p>
  <p>However, when I set <code>preferredFramesPerSecond</code> to 120 (and the respective Info.plist key to allow it), everything keeps up at 120fps, no problem:</p>
  <p><a href="https://i.stack.imgur.com/7Zr7s.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7Zr7s.png" alt="120fps, no problem." /></a></p>
  <p>So, clearly my update logic is executing well within the allotted time to maintain 60fps. Also, there's no issue maintaining 60fps on the simulator or my other test devices (iPhone 12 Pro, iPhone X, 1st gen. iPhone SE).</p>
  <p>This one has me scratching my head. Has anyone experienced this?</p>
  <p>Thanks!</p>
  <p><strong>Edit #1:</strong> Interestingly, I can reproduce the same behavior on my build just by limiting the frame rate in iOS’ Accessibility settings:</p>
  <p><a href="https://i.stack.imgur.com/t8HSG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/t8HSG.png" alt="Frame rate limit setting" /></a></p>