Someone also had this "SeaBIOS hangs" problem when they added the AMD OptionROM with cbfstool without specifying " -t optionrom " , and SeaBIOS hanged while trying to initialize it as a boot entry. Should be added like " ./build/cbfstool ./build/coreboot.rom add -f pci1002,6663.rom -n pci1002,6663.rom -t optionrom "