What happens if “two” vsync options are enabled at once? (RadeonPro, Starcraft 2)

Question

In StarCraft 2, some cutscenes are "animated" and don't use Direct3D, so when using RadeonPro's "Direct3D Tweak" vsync option (with triple buffering), these types of cutscenes aren't getting vsynced.

If I enable vsync via the "Visual" tab "Always on, unless app specifies", then these types of cutscenes do get vsynced. But then I'm concerned about having two vsyncs on at once. If I disable the "Direct3D Tweak" vsync, I'm concerned that I'll be losing triple buffering.

Does anyone know the effects of having two vsyncs on at the same time? Does one use triple-buffering while the other doesn't?

Answer 1

In theory, vysynch when enabled twice should have no real effect.

Vsynch locks framerate to that of the monitor. The first application would set the framerate to that of your monitor. The second application would also set the framerate to that of your monitor, but since it already would be from application 1, this would be redundant.

The mathematics behind setting the framerate is quite simple. You would be unlikely to notice the difference in taking the extra time to apply the same logic twice. However, if you want to talk technically, it will add a couple of milliseconds to the time it takes to apply each update.

Ultimately, it is unlikely that a human being would notice any difference between applying Vsynch once, or twice.