I have put AGESA 1.0.0.4 Patch B on several Asrock AM4 machines with different chipsets. X370, B450 (2 different mobos), X570. Used the following CPUs/APUs: 2400G, 3400G, 1600x, 3900x, 3950x in various mobos.
Now that we know about fixing the FLR problem with USB/HD audio passthrough I am unaware of any other problems with these BIOSes compared to the Pinnacle PI AGESA 1.0.0.6.
CPU and memory clocking appears to work just as well on older CPUs compared to older BIOSes, passthrough works well with new CPUs and I can passthrough more devices than before (did limited testing on this but the ACS CER cap options definitely improved things).
So I suggest that you shouldn’t be afraid of this BIOS update. But if you don’t have a new CPU not much point in updating anyway. Lots of new things to play with. BIOS now shows report window of RAM profiles, per ccx OC, faster boot, better iommu…
Note though that I DID see a new updated VBIOS on the 2400G. (I did a before/after VBIOS dump) So it is possible that they could have fixed an integrated graphics bug of some kind with new gpu firmware. Although I didn’t notice any changes with the IGPU after the update. You can still assign how much RAM you want to the IGPU on both 2400g/3400g on both old and new mobos.