Compatibility problems for new equipment are not always well explained, and information sometimes seems to be contradictory. This was the case with the X400 series motherboards and Ryzen 3000 processors, such as PCIe Gen 4. When Computex approached the end, AMD's senior marketing director Robert Hallock decided to explain rumors about this topic by announcing that "the pre-X570 boards will not support PCIe Gen 4, despite some technological innovations and social conversations that were spotted during Computex. This included snapshots of updated BIOS interfaces with AMD 300 and 400 series motherboards that allowed the user to switch between PCIe generations, including PCIe Gen 4. Hallock said however that these options are present in early BIOS updates and will be removed in final versions.
ASUS will make some of the main advantages of the X570 make sense, and cheaper CDs can benefit from the PCIe Gen. 4.
AMD took up this position saying "there is no guarantee that older motherboards can reliably meet stricter requirements of the Gen4 signal, and we simply can not have" yes, no, maybe "a combination on all the older motherboards on the market." Hallock explained that "The possibility of confusion is too big … the risk is too high." It now seems that some manufacturers like Asus disagree with AMD's claim that the equipment should be limited to "that either AMD Ryzen 3000 processors offer 16 PCIe 4 line for graphics cards and four more for the M.2 NVMe SSD, and seem to be partially useful because of the new BIOS in Asus motherboards with the X470 and B450 chipsets.
Momomo_US and ComputerBase.de provide a summary of motherboards that should come directly from Asian sources directly linked to Asuses, and display exact levels of compliance. It turns out that compatibility is pretty good, especially as for Memory M.2. It's strange, however, that the X470 boards work worse than the B450. This latest one can use multiple PCIe Gen 4 and PCIe Gen 4 cards. Some of the above mentioned Asus motherboards have already been tested. ComputerBase reports that the Chinese MyDrivers website tested the Gen 4 SSD in the Gaming TUF B450M-PRO. This configuration has reportedly reached about 5.0 GB of read and write performance of 4.2 GB / s, similar to what can be expected from the X570 motherboard with SSD PCIe Gen 4 M.2.