x86 is two well organized behemoths designing chips (including the base designs for most motherboards). On ARM, some SoC designers slap together IP blocks with

x86 is two well organized behemoths designing chips (including the base designs for most motherboards). On ARM, some SoC designers slap together IP blocks without fully understanding the implications. Not all SoC designers. But there are a lot out there, and not all have as high of standards as Intel and AMD. IIRC, the PCIe implementation on the SolidRun Honeycomb is quite good and can be used with GPUs.