So, I figured something else out which could be causing the issue:
Resizeable BAR is enabled under Linux, but not Windows.
In my head, this might make sense as to why I’m seeing a performance hit - as the Arch wiki says, enabling ReBAR can cause performance issues, especially with this particular setup
- GPU bandwidth limited to PCIe 3.0 x4 by Thunderbolt
- GPU (RX570) known for issues around memory bandwidth
- GPU (RX570) shouldn’t use ReBAR - no support from AMD for a GPU of this vintage.
Now the question is - how can I force disable ReBAR? Is there a kernel argument which would?
The FW BIOS doesn’t have an option to disable it