Hi, I have the following issue with my Samsung G80SD monitor (4K@240 Hz) on my NixOS installation with KDE.
I was previously using GNOME and the 240 Hz refresh rate worked correctly, as it also did when I switched my DE to KDE through the NixOS configuration file. However, after some system rebuild, the 240 Hz started to feel like plain locked 60 Hz across the entire system (even though my monitor reports it’s running at 240 Hz).
This happens regardless of the VRR setting (disabled, enabled, or automatic), and I can easily verify it on Blur Busters—those 240 Hz look exactly like 60 Hz.
On the other hand, 120 Hz works correctly (apart from some animation inconsistencies here and there), as do 60 Hz and 30 Hz.
I initially thought it might be related to this bug, but someone mentioned that it’s probably not, and that I should create a new bug report. I wanted to ask here first in case there’s a workaround or solution already, to follow good practices.
Thanks in advance.
Hi, I’m digging this topic since I seem to have the same problem. Did you manage to solve it ?
Just checked, out of curiosity, using glxgears (on Arch).
> glxgears
Running synchronized to the vertical refresh. The framerate should be
approximately the same as the monitor refresh rate.
501 frames in 5.0 seconds = 100.130 FPS
483 frames in 5.0 seconds = 96.600 FPS
494 frames in 5.0 seconds = 98.797 FPS
496 frames in 5.0 seconds = 99.198 FPS
486 frames in 5.0 seconds = 97.160 FPS
520 frames in 5.0 seconds = 103.832 FPS
526 frames in 5.0 seconds = 105.154 FPS
536 frames in 5.0 seconds = 107.031 FPS
532 frames in 5.0 seconds = 106.282 FPS
747 frames in 5.0 seconds = 149.329 FPS
1199 frames in 5.0 seconds = 239.657 FPS
1195 frames in 5.0 seconds = 238.947 FPS
1202 frames in 5.0 seconds = 240.030 FPS
1200 frames in 5.0 seconds = 239.818 FPS
1195 frames in 5.0 seconds = 238.803 FPS
1191 frames in 5.0 seconds = 238.191 FPS
With my 2 120Hz HDR monitors I get roughly 100Hz one slightly below and the other slightly above. The non-HDR 240Hz one seems fine here (the 149 FPS i got dragging the animation from one monitor to the other).
No, but it seems to be an issue more related to the Nvidia drivers and the monitor connection, since I also opened a thread on the Nvidia Linux forums and some people are experiencing the same problem across different distributions and desktop environments.
I can’t post links here (no idea why), but search for “I can’t reach 4K@240 Hz on my monitor via HDMI 2.1” on Google, the first result on the Nvidia Developer Forums is my thread if you’d like to add more details about your specific setups there, maybe it could help in resolving the issue or at least identifying the root cause.
In the meantime I switched back from TuxedoOS, on which it wasn’t working no matter what, to MX Linux on which it works out of the box with the Nvidia proprietary drivers.