Most x470 motherboards will require an older AMD CPU to be installed to update the BIOS to support the 3xxx CPU's.
There are some that have a BIOS Flashback feature that allow you to update the BIOS without a CPU installed.
Also the new MSI B450 MAX version boards will have a new bigger BIOS chip than the MSI non-Max boards and be ready for the 3xxx CPU's out of the box.
Here is a list of boards that have the Flashback feature:
ASRock (BIOS Flashback)
None!
ASUS (USB BIOS Flashback)
ASUS Crosshair VI Extreme
ASUS Crosshair VI Hero
ASUS Crosshair VI Hero (Wi-Fi AC)
ASUS Crosshair VII Hero
ASUS Crosshair VII Hero (Wi-Fi)
Gigabyte (Q-Flash Plus)
None!
MSI (Flash BIOS Button) [
View: https://www.youtube.com/watch?v=iTkXunUAriE
]
MSI B450 Gaming Plus
MSI B450 Gaming Pro Carbon AC
MSI B450 Tomahawk
MSI B450-A Pro
MSI B450M Bazooka Plus
MSI B450M Gaming Plus
MSI B450M Mortar
MSI B450M Mortar Titanium
MSI X370 Gaming M7 ACK
MSI X370 XPower Gaming Titanium
MSI X470 Gaming M7 AC
Note:
The MSI non-MAX boards have a 16 MB BIOS chip and are limited to a text based BIOS UI and may have issues with size limitations with newer AGESA versions.
This is a good reference for checking the VRM on motherboards to see how well they will handle the 3xxx CPUs:
https://docs.google.com/spreadsheet...IVNyMatydkpFA/htmlview?sle=true#gid=639584818