AMD of course announced their desktop Ryzen “Raven Ridge” APUs, which combine quad-core “Zen” CPUs with “Vega” integrated graphics solutions. One very interesting that that has caught the attention of many people is the PCI-Express interface. These chips feature only 8 PCI-Express gen 3.0 lanes for discrete graphics, this is in addition to 4 lanes for the chipset-bus, and 4 lanes driving the 32 Gbps M.2 NVMe slot. So this means that any discrete graphics cards plugged into the PCI-Express 3.0 x16 slot will run at PCI-Express 3.0 x8 speeds.
While many tests have shown that the performance loss between gen 3.0 x16 and gen 3.0 x8 is negligible, this could be an issue for users who were planning to combine these processors with AMD X370 chipset motherboards. The second x16 slot on these motherboards will not work and without at least x8 bandwidth there is no possibility of NVIDIA SLI functioning, even on boards that have SLI certification.
To be fair Raven Ridge is not really marketed towards people who plan on using X370 motherboards, but rather those who select B350 or A320 motherboards and value the presence of SoC graphics. One could also argue that this could make these chips mining resistant as you are not getting the full x16 PCIe lanes.