I'm having a tough time getting my Linux system to recognize my AMD 7900XTX as the primary GPU. Here's my setup: I have an AMD 5800x CPU, a B550M "Mortar" motherboard, and two AMD GPUs: a 7900XTX in the top PCIe x16 slot and an RX 560 in the bottom slot. For monitors, I have two 4K displays connected to the 7900XTX via DisplayPort, and a 1080p display connected to the RX 560. The RX 560 was added because my 7900XTX only has two DisplayPorts, and using HDMI causes crashes on my Linux distros due to driver issues.
The issue is that when I run games, it appears that the RX 560 is being used as the primary GPU instead of the 7900XTX, which is odd since my games are launching on the monitor connected to the 7900XTX. I've tried everything from setting udev rules, adjusting settings in KDE, experimenting with environment variables, and even switching distros, but nothing seems to work persistently. I had some success in Linux Mint with X11 by altering the xorg.conf to set the 7900XTX as the primary, but I still prefer to use Wayland for its advanced scaling features.
What I really want to know is, how can I configure Wayland to use the 7900XTX as the primary GPU? Alternatively, is there a way to work with different scaling settings for my 4K and 1080p monitors in X11?
2 Answers
Check your BIOS settings—sometimes there's a configuration that controls the order of priority for PCIe devices. The way your system detects these may not reflect the physical installation order. Since you mentioned the 7900XTX is recognized differently in `lspci`, it might be queuing it incorrectly during boot.
Given your situation, you might want to report this as a bug, but make sure to mention whether it's a Wayland, kernel, or AMD driver issue. It can be hard to pinpoint exactly where the problem lies, but sharing logs and detailed info on your setup could help. It’s great that you’re committed to sticking with Linux; keep digging and you might find a solution!
I checked my BIOS settings, but there's no option for adjusting the GPU order or priority. It’s an MSI Click BIOS 5, and I noticed the RX 560 is listed first even though the 7900XTX is in the top PCIe slot.