I had been using a Gigabyte AORUS FO32U2 monitor at 3840x2160@240Hz via a DisplayPort of my RTX 4080 Super.
However, the maximum refresh rate allowed recently is only 4K@200Hz.
Another interesting issue is that there’s no audio via DisplayPort at 200Hz, only at lower refresh rates. The next lower step is 165Hz on my system.
It’s as if my DisplayPort is bandwidth limited, so instead of 240Hz, now 200Hz is the maximum, but I have to lower it further to 165Hz to have audio. I have the same hardware, the same cable, everything.
I temporarily downgraded to the previous Linux Mint 22 version and to the Nvidia driver 550.127.05 to see whether 240Hz is available again without audio issues. Still, the same limitations applied as now, so I don’t know what went wrong.
I’d really appreciate any insight you can provide!
Most reasonable guess would be the cable, as you’re at the limit of DP 1.4a with DSC, so even a minor issue with the cable is going to downgrade things.
I’ve tried two additional DisplayPort cables, and the issue persists. I’ve even rebooted my PC, assuming that DisplayPort bandwidth may be renegotiated upon bootup.
I’ll keep using the original cable via which 240Hz used to work.
How can I retrieve the current DisplayPort bandwidth used? There must be a way to troubleshoot this issue.
Don’t know any off hand. I think at one point nvidia-settings showed monitor info, maybe it still does under X11. You could try booting into a live distro to see if the option is available. If it’s not, it’s almost certainly a hardware issue.
Thanks to this comment, I figured it out! I just had to set the DisplayPort version from 2.1 to 1.4 in the OSD of my monitor. Must have been changed since the last time.
I have the FO32U2P model with the same issue, but I don’t recall a setting to switch DP version. Where can I find that setting? Also wanted to note, I am using a certified DP 2.1 cable.
Thank you, I found the setting. I’m running a 4090 which is also DP 1.4. What’s odd is I can get 240hz to work on version 2.1 if I toggle off/on Freesync Pro or unplug/plug in the DP cable, but it goes back to 200hz after every shutdown or reboot of my PC.