Security is one thing, the fact to be able to use the equipment we bought as we need is another.

My Mac Pro are a 2009 Mac Pro 4,1 and a 2010 Mac Pro 5,1. So to put it more simply, my question here is to know if it is possible ( easily ) to downgrade the EFI / Firmware ( and SMC if needed ) of a Mac Pro, at least to revert it to the original one which was in the Mac when it was released ( or any in between if needed if there was some ). Īlso, is it possible after upgrading a Mac Pro 4,1 to 5,1 ( upgrading the EFI/ firmware / SMC) if ever i encounter compatibility problem to boot with older OSX or hardware, to revert the EFI/ firmware back to 4,1 ? I am trying to find some infos about backward compatibility with older OSX ( see my other topic if needed, about High Sierra backward compatibility with older OSX) after upgrading the Mac Pro EFI/ Firmware like when installing High Sierra ( It asks for EFI/ Firmware update ), if i want to go back to an older OSX or simply boot with any older OSX ( down to 10.6.x Mountain Lion ) and if it is possible to revert to previous / original EFI/ Firmware / SMC if needed.

Mac mini mid 2010 bios update