S5520HC EFI Optimized Boot

Hi,

I have difficulties with EFI Boot.

Long story short:

Having BIOS revision R0064 I'm trying to boot OS V 10.11 El Capitan.

The process is trail/error, so I need an easy way to change the BIOS Boot mode between MBR/EFI.

It is because I'm not sure I have proper disk for EFI boot, although I've got an OS X 10.11 installed on the machine and it doesn't boot in MBR mode, but if I set EFI Optimized Boot and try to boot my installation I don't have an success. The error code is 0xD6 - Trying boot selection.

The worst thing is I don't have an access to the BIOS Set Up at all so, I have to recover or update the BIOS to get the system working.

Any ideas?

Thanks.