I created a demo system by following the https://pve.proxmox.com/wiki/Pci_passthrough#GPU_OVMF_PCI_PASSTHROUGH_.28recommended.29 documentation.
However I find the _ recommendation _ to use PCI over PCIE strange... While some cards may function with PCI only, it is certainly not the standard test-case and there are many corner cases where the driver could reject loading due to missing PCIE feature / capability. I won't speak specifics, but one card I tried predictably failed on PCI. The newer the card, the less likely it is to function in PCI.
If there is valid rationale behind choosing PCI, I would love to hear it
I would recommend PCIE as the suggested default for graphics cards.
Disclosure: I work for AMD on Windows device drivers.
However I find the _ recommendation _ to use PCI over PCIE strange... While some cards may function with PCI only, it is certainly not the standard test-case and there are many corner cases where the driver could reject loading due to missing PCIE feature / capability. I won't speak specifics, but one card I tried predictably failed on PCI. The newer the card, the less likely it is to function in PCI.
If there is valid rationale behind choosing PCI, I would love to hear it
I would recommend PCIE as the suggested default for graphics cards.
Disclosure: I work for AMD on Windows device drivers.