Exact refresh rates

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silikone
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Joined: 02 Aug 2014, 12:27

Exact refresh rates

Post by silikone » 25 Sep 2014, 21:10

How precise are the specified refresh rates, and what is the deal with 59Hz/60Hz modes? I believe CRTs approximated refresh rates at different timings, leading to varations depending on the display resolution. How does this affect Vsynced applications? For example, if a 60 FPS capped game was Vsynced to a VGA/NTSC display at slightly below 60Hz, what would happen if Vsync was enabled with a display mode that refreshed slightly above 60Hz?

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RealNC
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Re: Exact refresh rates

Post by RealNC » 26 Sep 2014, 08:14

Refresh rates are very precise. The used default modes can very a bit from monitor to monitor, but otherwise, they are precise. If a monitor ships with a 60.019Hz mode, then it's gonna be 60.019 every time. It is very precise and is not going to fluctuate.

A 60FPS capped game being vsynced to a higher than 60Hz display mode is going to display the same frame twice (or more) at specific intervals. This interval depends on the refresh rate. For example, at 61Hz, a frame is going to be displayed twice once per second. At 120Hz, every frame is going to be displayed twice.

If the game is being vsynced to a lower than 60Hz mode instead, then the game is going to be capped to that refresh rate as a side-effect of vsync. If you run the game at a 57Hz mode for example, then your game will effectively be capped to 57FPS, even if you've set the frame cap to 60.
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