Today I started up my X79SI and it couldn't start from my SSD, and I've been unsuccessful to get it to boot from DVD or USB drive either.
All of the drives can be seen in BIOS, it just doesn't seem to now how to start loading Windows.
Apart from booting off the different media types, I've already upgraded to the latest BIOS (594) via F7, and done a BIOS settings reset via F9 as well.
The exact error message I get is
A bootable device has not been detected.
Please refer to the Product Guide at http://support.intel.com/support/motherboards/desktop http://support.intel.com/support/motherboards/desktop
Any other suggestions?
It turned out to be a problem with UEFI. I started making headway when I discovered that F10 allowed me to boot into everything except the SSD, but I could still boot off the SSD if I chose the UEFI option. Then it was a matter of using diskpart, bootrec, bcdboot and bcdedit.
Not sure what caused the problem, but happy to be able to resolve it.