Apparently, only AMD’s top-of-the-line X370 chipset will support NVIDIA’s SLI technology. The mid-range B350 chipset lacks SLI support but retains CrossFire compatibility, while the low-end A320 chipset will not have any support for multi-GPU technologies. While this may seem a move by AMD to purposely gimp NVIDIA products on its platforms, it stands to reason that even enthusiasts tend to stay away from multi-GPU solutions and their associated problems.
Also, AMD will surely want to avoid giving NVIDIA more money by giving the “SLI Tax” on every chipset they ship. By limiting SLI support to its highest-end chipsets, AMD removes some expenses from licensing efforts, while keeping SLI support to the higher-end chipset, who’s users likely to afford to get a multi-GPU config.
As of now, some details remain unclear as the NDA still up, the overall feature-set and compatibility differences between AMD’s upcoming AM4 chipsets, but it would seem that only AMD’s X370 chipset manages to leverage the full 20 PCIe lanes (18x if you run 2x SATA connections) delivered by AMD’s Ryzen CPUs. This would look like a way for AMD to impose a high-end motherboard on to its users, by limiting the number of PCIe lanes available on lower-end motherboards, so those who want more PCIe lanes have to go with X370 chipset. We will keep you posted as any new information come up on this matter.