While AMD has done a great job of maintaining motherboard compatibility with new generation processors, none of the previous-generation AM4 motherboards featured official PCIe 4.0 support, not even from the storage and PCIe controlled by PCIe 4.0 compatible CPUs. Enter B550, the more value-oriented little brother of X570. While the B550 chipset is PCIe 3.0 only, B550 motherboards support PCIe 4.0 from the CPU to the primary PCIe slot as well as the primary M.2 slot (dependent on a PCIe 4.0 ready CPU).
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