yes you can use biosflashback to update your bios without a cpu, to use this feature you have to convert the bios file from the asus website, go to the motherboard model page and under support there is a utilities tab where you can find the bios converter just follow the instructions and you're done !
i only use this method to update my bios whenever is possible as it is for me the best way to do so
here you go (bios renamer)
when you see the led in the bios flashing its updating when it turns of its all done
oh format with FAT 32 usb stick or it wont work