https://bugs.kde.org/show_bug.cgi?id=504303
Bug ID: 504303
Summary: 240 Hz monitor feels like 60 Hz system-wide
Classification: Plasma
Product: kwin
Version First 6.3.5
Reported In:
Platform: NixOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: performance
Assignee: kwin-bugs-n...@kde.org
Reporter: merkurio...@hotmail.com
Target Milestone: ---
SUMMARY
Hi, I posted this on [https://discuss.kde.org](https://discuss.kde.org) but
didn’t get any response, and I’m also not exactly sure which component this
falls under so I posted it under “performance", feel free to move it to the
most appropriate category.
I have the following issue with my Samsung G80SD monitor (4K@240 Hz) on my
NixOS installation with KDE Plasma 6.3.5:
I was previously using GNOME and the 240 Hz refresh rate worked correctly, as
it also did when I switched my DE to KDE Plasma through the NixOS configuration
file. However, after some system rebuilds, the 240 Hz refresh started to feel
like plain locked 60 Hz across the entire system (even though my monitor
reports it’s running at 240 Hz, as well as the Nvidia X Server app and even the
KWin FPS tool under Desktop Effects).
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[https://bugs.kde.org/show_bug.cgi?id=485927], but someone mentioned that
it’s probably not, and that I should create a new bug report, so here I am.
Thanks in advance.
STEPS TO REPRODUCE
1. Change the refresh rate to 240 Hz under screen settings
OBSERVED RESULT
Everything feels and behaves like a fixed 60 Hz refresh rate, easily verifiable
on Blur Busters and with anything being rendered on screen (even the mouse
pointer), despite everything indicating that the display mode is set to 240 Hz
(including my monitor’s own OSD and even the KWin FPS tool).
EXPECTED RESULT
Everything should feel smooth and run at 240 Hz, which is not the case
(choosing 240 Hz and 60 Hz feels identical — I have to set it to 120 Hz to get
a high refresh rate, but that doesn’t take full advantage of my monitor’s
capabilities).
SOFTWARE/OS VERSIONS
Distro: NixOS
Linux kernel: 6.14.6
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
ADDITIONAL INFORMATION
1) The problem seems to occur both in Wayland and X11 sessions, although I only
use Wayland now.
2) In the beginning (when I switched from GNOME to Plasma using the NixOS
config file), it works at 240 Hz with no major problems, but after some package
installation/system rebuilds, this locked 60 Hz-like situation appears.
3) 120 Hz, 60 Hz and 30 Hz refresh options works properly.
4) I have a powerful PC rig with a RTX 4090 and the latest 570 drivers, 240 Hz
works fine on Windows 11, it's not a low-spec hardware related problem.
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