As the title suggests, I’ve been dealing with this issue since I started using Linux as my main operating system.
The only way I can achieve 240 Hz at 4K resolution in Linux on my Samsung G80SD monitor is by using a DP 1.4 cable, which introduces artifact flickering when selecting either 120 Hz or 240 Hz as mentioned in this thread. This happens to me on both Linux and Windows.
With the HDMI 2.1 cable however, the connection is perfectly stable and solid up to the entire 240 Hz in Windows 11, but only up to 120 Hz in Linux. When I select 240 Hz in KDE’s display settings panel, the entire system behaves very sluggish, as if it were running at exactly 60 Hz just as I confirmed using the Blur Busters’ TestUFO (even though everything indicates that internally it’s running at 240 Hz timings, including the monitor’s OSD and even KDE Plasma’s FPS display tool).
Is this a limitation of the HDMI 2.1 protocol on Linux? I understand there were issues with AMD, but I’m not sure what the current state is with Nvidia.
System info:
Distro: NixOS unstable channel
Kernel: 6.15
Nvidia driver: 575.57.08
DE: KDE Plasma 6.3.5
Monitor: Samsung Odyssey G80SD
The monitor is a Dell AlienWare 4K 240Hz. As soon as I set the Display Configuration to 240 Hz, most applications on the whole system, including a different monitor running at 144Hz, become sluggish. Feels like the whole graphics pipeline is clogged, probably because it is.
I don’t have an HDMI to DP adapter to spare in testing this at the moment. Maybe 4K 240Hz is a no-go on Linux right now.
I’ve got the same problem on Samsung G80SD. Can set 240Hz but it feels like animations looks like 60 fps. Display is connected via HDMI 2.1 and in Windows it’s working fine.
Distro: Fedora 43
Kernel: 6.17.10-300
nVidia driver: 590.44.01 (tried also stable release, but problem persists)
Yes, and it is enabled. I can select 240Hz refresh rate and monitor says that it is 240Hz but it feels like it is 60Hz. Resolution doesn’t matter I checked that on 1440p, 1080p and same behaviour is when it is on 240Hz. Although 120Hz works fine.
There’s definitely an issue with high refresh rates on the current drivers.
My problem is similar but not quite the same.
Refresh rate is fine at 240hz right up until my g93sc sleeps. After that the refresh rate drops to 60hz and is locked until I reboot the monitor or the computer.
DisplayPort causes the monitor to not wake up at all. Happens on gnome and kde on both Cachy and Bazzite
I solved this issue (If I am remembering correctly) in a multi monitor setup by setting the display scaling size in the native OS setting to non fractional. AKA monitor is set to exactly 100% or 200% , not 125% or 150%. I then ensured that both monitors refresh rates were set to have a common denominator equal to each other. IE Alienware 240hz monitor set to 240hz, and additional second monitor set to 120hz not 144 or 165. Also either both monitors had HDMI enabled or both had HDMI disabled. and I either had both monitors with GSYNC-VRR-Adaptive Sync enabled or disabled. I’ve found that most of my multi monitor issues have boiled down to the two installed monitors having conflicting setting configs. I am almost certain this resolved my issue with this. LMK if it solves your issue.