144 Hz monitor detected as 120 Hz, runs at 104 Hz

[rph]

I'm trying to get my Acer XV340CK monitor to run at 144 Hz, but it's not being detected properly. My graphics card is a Sapphire Radeon R9 280X, and I have it connected with a mini DisplayPort to DisplayPort cable. This is on Linux, Fedora 32. I'm using the amdgpu (not amdgpu-pro) driver. The only refresh rate options I'm given are 60 Hz, 85 Hz, and 120 Hz. If I try lower resolutions I can get various lower refresh rates, but nothing above 120. If I select 120, according to the monitor OSD and testufo.com, I only get 104 Hz.

 

I've also tried three different HDMI cables, including the one that came with the monitor, on the desktop and a Dell Precision 5520 laptop. On all of those, I only get 30 Hz at the full 3440x1440 resolution. If I lower the resolution to 1080p, I can get 60 Hz. According to the user manual, the monitor should support 100 Hz over HDMI and 144 Hz over DP.

 

How can I get this to run at 144 Hz?

[Zoltus]

check the monitor settings if there is anything, so use monitor buttons to accesss the settings

[rph]

There's nothing in the OSD to change refresh rate. The only settings I see that might affect refresh rate are using DisplayPort 1.4 or 1.2, switching "Overdrive" between Normal and Extreme, and turning DDC on/off. I've tried all of these and I don't get any new options under refresh rates in system settings.

[rph]

Update: I tried booting into Windows and even with the official Acer driver installed I'm only getting options for 60 Hz and 85 Hz on DisplayPort.

 

Second update: Today I had a chance to test this with a full size DisplayPort cable on a Thunderbolt dock connected to the laptop. It runs at the full 120 Hz with that setup, but I still can't get it to detect the 144 Hz maximum. I also tried connecting the mini DisplayPort cable I've been using with my desktop to the dock and it also runs at 120 Hz, so the cable isn't the limiting factor.

 

I'm also able to get 60 Hz over HDMI with the Thunderbolt dock.

[rph]

Sorry to keep bumping this thread, but I solved it. Either my graphics card just isn't powerful enough for 144 Hz @ 3440x1440 or it has too old of a DisplayPort standard for its mini DisplayPort ports. Either way, I'm able to get 144 Hz at 1080p using xrandr, even though the option isn't exposed in the GUI display configuration.