sorry, my fault, i wanted to write 3900x not 3990x, the 3900x is am4 but thanks much becsuse i didnt know thataNo....
The B350 is a socket AM4...(you can research today's R9-3900X if you wish.., or, wait two more months for R9-3950X?)
The 2990X and upcoming 3990X are/will be , respectively, socket TR4, a much larger socket/chiplet package used on the X399 chipset....
a 12 core cpu on stock speed will be enough, maybe i will underclock itIf you update the bios to the latest version the 3900x will work.
You will want some airflow over the vrms and it lead to high vrm temps and a little lower cpu clockspeed, but it will work.