AMD’s Ryzen 5000 processors are officially supported on the 500 series boards, with some board partners releasing beta BIOSes for the 400 series boards as well. However, there weren’t any official firmware releases supporting the Zen 3 CPUs on the older 300 series boards, including the B350, A320, and X370 chipsets. However, thanks to certain enthusiasts, you can now run the new processors if you have an X370 ASRock board.
The boards supported include the X370 Gaming K4, X370 Gaming X, X370 Killer SLI, X370 Killer SLI ac, X370 TAICHI, and X370 Professional Gaming. The editors over at HKEPC tested the beta BIOSes and they seem to function normally., passing the POST, boot, and a burn-in test. The performance results are also in line with other boards. However, since this is a beta BIOS, there may still be minor bugs here and there, so be informed.
You can download the beta BIOS for the ASRock X370 boards here.