This is a separate question related to a problem I’m facing with my monitor when using DisplayPort cable. For those interested in the full discussion on that you can find it here:
The gist of the situation and my question now: My monitor won’t work properly when connected to a DisplayPort cable. HDMI works without any issue but has a major limitation that’s been forcing me back to DP: It only runs at 120 Hz instead of the 144 Hz supported by the monitor. When I looked at this I remember reading it’s a hardware limitation, due to my model using an older HDMI version which doesn’t allow the bandwidth needed to do 144 Hz @ 1080p resolution. My monitor is a Viewsonic VX2458-C-MHD, here’s its official page and the product page of the store I ordered it from:
I’m now questioning this statement after someone who has the same monitor told me you can in fact do 144 Hz on HDMI not just DP. I was told the 120 Hz cap would be a mere limitation in the AMD driver instead. This would help me greatly as I no longer need to keep trying to use DisplayPort and risk damaging my hardware if that’s the case.
But how do I lift this limit? Specifically how do I do it on Linux? I haven’t used Windows for a decade and don’t plan on touching it again, my OS is Manjaro. The KDE display settings offer me 144 Hz on the problematic DisplayPort but only 120 Hz on HDMI. Is there a command I can use on either the X11 or Wayland session to force the system to let me try the full refresh rate and see if it works? I know xrandr lets you do weird things on X but no idea if I can use it to force the full resolution. Could someone please post the steps required to try this? Thank you.
Following the final command the monitor fell in an endless loop of going to sleep, waking up, saying there’s no signal, going to sleep again. The 144 Hz option appeared in the system settings as well but had the same result. What do you think is causing that?
As this guide shows my monitor is in fact meant to support 144 Hz even on HDMI. My HDMI cable is 2.0 compatible so it shouldn’t be a version limitation either.
Same problem: Monitor enters a loop of saying there’s no signal for 5 seconds then going in standby for another 5 seconds. Everything says this should be supported so it makes no sense.
Solution found and it is working! Cheers to MichaelDeets on Reddit for his help. The issue with the xrandr command is that cvt and gtf produce excessive clocks by default. In their place I used this calculator and came up with a safe minimum that actually works:
The messy workaround should be simple: Just add this and the other xrandr commands to ~/.profile and the whole thing will be automatically applied on login. But why is this even needed, why can’t the system automatically detect the proper settings for 144 Hz as it does for 120 Hz and below… is this a bug worth reporting with the Linux kernel or AMD developers?
Another important question: Eventually there may come that faithful day when KDE users can use the Plasma Wayland session bug free. What’s the equivalent to xrandr for Wayland? What commands do I use in its case to set and use a custom mode in the same way?
