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I'm having a slight issue with the GLFW library and VSync. I'm testing a very basic GLFW program on both my integrated processor and my "high performance NVIDIA processor".

When running the program on the integrated processor with the VSync callglfwSwapInterval(1), I get around 16 ms/frame (~60 FPS), as expected. However, when running the same program on the NVIDIA processor with the same VSync call, the frame rate drops to around 30 ms/frame (~30 FPS). I tried testing the program without the glfwSwapInterval call, and it behaved as expected when run on the integrated processor (less than 1 ms/frame). When I tested this on the NVIDIA processor, I was getting around 24 ms/frame, which definitely isn't correct. When running the program with the call glfwSwapInterval(0), both processors run as expected at less than 1 ms/frame.

At first I figured maybe this might be a GLFW issue, but I'm not quite sure anymore. I checked the settings for the NVIDIA processor, and they state that the VSync option is controlled by the application, as it should be.

Again this is a basic GLFW program with no draw calls whatsoever. Any insight into what could be causing the issue would be much appreciated. I can provide more information if needed.

nprof50
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  • What sort of display are you using? 24 Hz and 30 Hz remind me of a television... the display driver may be optimizing for multi-monitor / TV output. Also, have you tried a swap interval of -1 (Adaptive VSYNC)? – Andon M. Coleman Apr 14 '14 at 16:25
  • The display is an Acer monitor with a refresh rate of 59 Hz. I adjusted it to 60 Hz, and the problem stopped occurring, even when I set it back to 59 Hz. While the problem is no longer occurring, it would be nice to know why it occurred, even though the refresh rate is almost 60 Hz. Thanks again for the help, I appreciate it! – nprof50 Apr 14 '14 at 18:57

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