AMD's next-generation X570-series motherbaords will be debuting in the coming months with PCIe 4.0 technology, but current-gen boards are also seeing support for the new PCIe standard with GIGABYTE X470 and B450 boards receiving BIOS updates enabling support when paired with a new Ryzen 3000 series processor.
GIGABYTE's new BIOS updates for X470 and B450 motherboards include PCIe 4.0 support, with a post on Reddit by 'mVran' showing the F40 BIOS for the AORUS Gaming 7 Wi-Fi X470 has Gen 1/2/3/4 support. Then we have leaker Momomo_Us tweeting out that the F40 BIOS also adds PCIe 4.0 support to the B450I AORUS PRO Wi-Fi motherboard.
You will only get PCIe 4.0 support when you pair the PCIe 4.0-capable motherboard with a new Zen 2-based Ryzen 3000 series CPU. The first PCIe 3.0 slot on supported motherboards will operate at PCIe 4.0 speeds over the CPU PCIe lanes while the rest of the PCIe slots would still flow through the PCH as normal, but this will vary board to board so you will need to be careful.