While there is not a lot of information yet, I have not really heard where any of the tech sites really know how this works yet. I guess I can see where there can be a physical difference in the Zen3 architecture. What I don't get is the x5xx chipset requirement. If B550 can support it then x4xx should be able to support it too. All of pcie 4 features on B550 don't come from the chipset like on x570, they come from the CPU. So I would sure think it should work. That doesn't mean AMD will allow it to. My gut tells me that more often than not, a lot of features that don't get backward support really could work if they wanted it to.