Yes, the board requires a BIOS update: http://www.asus.com/Motherboards/AMD_AM3/Crosshair_IV_Formula/#CPUS
You need a supported CPU for updating the BIOS (update only the last version, no need to update all newer versions) or a new BIOS chip for replacing the board's one.
SO, i use my phenom II installed to update the last bios; right after the reboot update i turn off the pc and install the fx bulldozer processor and turn on the pc? is that the path i must follow?
sorry about my stupid questions, but i´ve read in the bios references that must not be used with AM3 processors. that´s my i´m asking this.