This thread was never about how q35 is faster or lower latency, it’s about those of us that do use it either for improved compatibility with pass-through or whatever can obtain optimal performance from a q35 system.
Please see: https://wiki.qemu.org/Features/VT-d
These features are only available on the q35 platform and some of us require them to either get optimal performance out of our hardware, or even get passthrough to work properly in the fist instance.
The Idea that UnRaid will remove Q35 or even warn about using a newer platform topology that even the Qemu developers are trying to push is idiotic. Not only are they going to make it harder for their users to use UnRaid where Q35 is a requirement, it is going to make people shy away from the option when it is completely valid and may for their particular configuration yield performance gains.
Also we have evidence that shows that when the driver detects a link speed of 0x, or that it’s not on PCIe (ie, i440fx), it programs the SoC differently. Evidence both through benchmarks and the AMDGPU source code in the Linux Kernel which has an todo to implement the PCIe 3.0 specific configuration in: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/amd/amdgpu/soc15.c#L446