I will only change cpu and keep other parts.
Upgrade from 2700x to 5800x3d.
I have b450 tomahawk max with agesa 1.2.0.7.
Is there anything I need to do after I change cpus?
Not typically. You usually only need to reinstall if you change the motherboard, or you replace your storage.
I did see that answer on google ahah. ofc we need to install windows if we remove ssd or hdd where windows is installed.
Also, don't forget to look at the product page for the board to see which BIOS you need as the B450 doesn't natively support Ryzen 5000.
agesa 1.2.0.7 did add support for 5800x3d
I did find information that if you have ryzen 7900x3d or 7950x3d and you want to change cpu and install 7800x3d you need to reinstall windows.