Its well possible it just works by flashing the latest B450 Pro4 BIOS 4.80 onto the AB350 Pro4.Thead for requesting Bios mod for ASRock AB350 Pro4 for support Ryzen 5000.
Are you sure?Did you see any screenshot or actual working board with flashmod.Its been strange that the working flashmod on Taichi is blocked/broken getting errors 4d and the other is working.I would like to see screenshot of the actual agesa working.I had read it before 4 months but I never seen any actual user posting anything else .I have flashmod my Taichi x370 but zen3 is not working.
The guy in the reddit postet a screenshot:Did you see any screenshot or actual working board with flashmod.Its been strange that the working flashmod on Taichi is blocked/broken getting errors 4d and the other is working.
its very strange that our flashmod in Taichi does not work and with a flash on B350 to actual work.Your Asrock x370 itx has beta bios as our P6.61/6.62 that working.I would like to see other users with B350 that flashmod with latest agesa 188.8.131.52 and working.Even in ASUS forums that flashmod they made it with 184.108.40.206 not with latest agesa.The guy in the reddit postet a screenshot:
I also discussed with him and I have no reason not to believe him. On the other hand, I have tested it myself with a 5800x on my AsRock X370 ITX and it works perfectly with Zen2 but no boot with Zen3.... very similar to the Taichi 4D Error.
Could be that it works with B350 Boards but not with X370 Boards.