Question about AMD Ryzen 7 1800x

Level1techs have a few videos and articles on this. As I understand it, you need an X370 chipset to be able to split the two GPU PCIe slots to 8x/8x, B350 does not support this. Also, in older BIOS versions before 1.0.0.6 AGESA microcode the two GPU slots were in group 2, since this version fixed. For better info Google Level1Tech and IOMMU, you should be able to find everything you need to know.