I have a fairly new set up , about 1 month old . My boot drive is about 5 months old , a 500gb ssd. About a week ago I was messing with the ram expo and when I went to restart the bootable drive was no longer available. I set all my BIOS settings back to default and here a week later I am still having the issue of no bootable device found. I have two other drives for storage and when disconecting the other two storage devices it seems to find the new ssd with the OS loaded on it. Other than that I am constantly having to switch from Legacy to OPROM and back to legacy every time I boot up.