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Incorrect frame rate on a 240Hz monitor ( demo)

Good afternoon everyone,

The setup is a monitor at 240Hz connected to a laptop. I’m trying to run an experiment at 240fps but before I’m running timing demo to measure monitor frame rate. My issue is that I can only get a time by frame mean of approximately 4ms (corresponding to 240Hz) with very little window size, some example:
800800pixels --> 5.9ms
400 --> 4.6ms
200200 --> 4.3ms
100 --> 4.3ms
19201080 (fullscreen size without fullscr=False) --> 12.6ms
1080 (fullscreen size with fullscr=True) --> 12.6ms

Do you know what should I do in order to get a full screen running at 240Hz?

Thanks in advance for your help!


  • my screen laptop is disable
  • Without any success I’ve tried in visual.window():
    - wintype = “pygam” and “pyglet”
    - fullscr=False and True
    - allowGUI = False and True
    - waitBlanking = False and True
  • When I set my monitor at 144Hz I can observe approximately the same effect.
  • Monitor FPS counter give me the FPS I’ve set in Advanced display settings (the good one).

Monitor: ASUS VG279QM
Laptop: Dell latitude 5400
Processor: Intel® Core™ i7-8665U
OS: Microsoft Windows 10 Education
Graphics: AMD Radeon 540X
Connection between the laptop and the monitor: adaptor USB C to DisplayPort 4K@60Hz
PsychoPY version: v3.1.0