If you have an Intel board with running any 290/390/x, you may experience boot problems in certain cases. Please see below for a list of fixes.
Do not use an R9 390 in the gpu0 slot. Instead, use another GPU (example, R9 380).
Use a 16x16x ribbon riser in the gpu0 slot.
Use onboard video:
set PRIMARY GRAPHICS to ONBOARD.
set SHARE MEMORY to 32MB.
NOTE: If you use onboard video, POST will occur on onboard video, and the ethOS desktop will be displayed on gpu0.