today I updated my DH77DF BIOS from 102 to 104 in order to check, whether UEFI support has been improved or not. But I faced a bootloop bug. You can reproduce it, when you enable "UEFI Boot" and disable "Legacy Boot". The display doesn't show any information. Hitting blindly F2 (to enter BIOS) during boot causes the machine to reboot. If you don't press anything, the machine will eventually boot the OS. But still, no display at boot and no possibility to enter BIOS. The only way to fix: configure mainboard jumper to "Maintenance Mode", enter BIOS, enable "Legacy Boot", shutdown, configure mainboard jumper to "Normal Mode" and reboot. Seems to be BIOS bug - it did not exist in BIOS 102, so it's something new. Would love to see it fixed in the upcoming BIOS versions.
//Edit: these two fixes look suspicious - probably caused this bug.
BIOS 103: Fixed issue where system does not boot to the operating system when UEFI Boot is enabled.
BIOS 104: Fixed issue where system hangs on boot after BIOS update if UEFI Boot is enabled.