I am currently running Sabayon 3.10.0 with Grub2 on an external usb hd, dual booting with Windows 8... (I believe Grub2 is on my mbr on usb hd), & the "new" uefi bios. I am able to boot by turning off (disabling) "secure boot," & enabling "legacy." My cpu is an AMD64, HP Pavillion desktop, with 8GB ram, 2TB hd (which I have shrunk the Windows 8 os partition to 1 TB, in the hopes of installing Gentoo on the other TB partition (which has not yet transpired).

I have been trying to research ways to simplify the boot process... there is a wiki article, specific to uefi & Sabayon... but it starts of with:

"This content is outdated! Sabayon now supports UEFI and UEFI Secure Boot out of the box."

http://wiki.sabayon.org/index.php?title=UEFI_Boot

When I installed Sabayon, from the liveDVD, it would not (apparently) install Grub (it may be possible that the initial install was not Grub 2, that is I think it's possible Grub2 was brought to me by a recent "update" of my software) on to the efi partition (in my case /dev/sda2).

So, though I may need to go to other sources for further reference in these regards, wondering if any one in the Grub community has any pointer, advice, links, etc. that may help clarify... (i.e., is Grub relevant to uefi, etc.?).

Thanks much,

Henry