You are using a current UEFI vbios (TV308MH.100) so it#s not a vbios issue. System ram is a kit of 2x8GB or 4x4GB? Kit or separate sticks?
Try running unigine valley benchmark at Ultra settings/Extreme HD: https://unigine.com/products/valley/download/
Try running unigine valley benchmark at Ultra settings/Extreme HD: https://unigine.com/products/valley/download/