I've got my 2820 box recently, and has upgraded bios to the latest version, 0038.
Have installed FreeBSD-10.0-RELEASE-amd64-memstick.img successfully (legacy boot mode),
But when the system reboot, the BIOS simply said cannot find bootable device or triggered a PXE boot (if enabled).
It seems that the bios cannot recognize fbsd's bootsect.
The problem exists after reset/clear/update the BIOS in any methods.
However, an Ubuntu-14.04.01 installation (test with legacy boot mode) works.
Finally, I find out that downgrade to 0032 do make the BIOS recognize FreeBSD and can boot into it.
(under legacy boot mode)
Steps to reproduce on my box:
Hello Adios, thank you very much for contacting us.
About your situation, please bear in mind that Intel® NUCs are designed to host Microsoft(R) Windows operating systems, please refer to the following link: http://www.intel.com/support/motherboards/desktop/sb/CS-034034.htm
Since FreeBSB-10.0 is working fine when using BIOS version 0032, I would recommend keeping this BIOS if you decide to continue using this operating system.
I can share this information with our developers as a heads up but please be aware that we cannot offer a solution for this problem.