I have been struggling with the MB for a month now, trying to get linux EFI booting to work. Fedora, Ubuntu, Debian and Arch will not boot. I managed to get Arch to boot by copying the loader to \EFI\boot\ directory, but if you put it anywhere else it will not work. I have tried all the efibootmgr commands, I have run shellx64 and used the bcfg boot command to set the boot location, but the bios, latest being 51, will not recognize the variables set by either of these methods. So, only booting with the .efi files in \EFI\boot\ work with this bios. Even though the variable is set in NVRAM, it will not boot. Only if the refind directory is renamed to \EFI\boot\ and the refined_x64.efi renamed to bootx64.efi am I able to get the system to boot. It seems only the auto detected boot efi's actually work.
[root@archrouter ~]# efibootmgr -v
BootCurrent: 0000
Timeout: 10 seconds
BootOrder: 0000,0001
Boot0000* Arch Linux (rEFInd) ACPI(a0341d0,0)PCI(1f,2)03120a000000ffff0000HD(1,800,1e8000,dd6faf42-e8b6-4b83-ba28-e3c3c4b019b3)File(\EFI\refind\refind_x64.efi)
Boot0001* UEFI : SATA : PORT 6G 0 : WDC WD7500BPKT-22PK4T0 : PART 0 : OS Bootloader ACPI(a0341d0,0)PCI(1f,2)03120a000000ffff0000HD(1,800,1e8000,dd6faf42-e8b6-4b83-ba28-e3c3c4b019b3)AMBO