My was also working until i updated to 1502 and now I can't downgrade since the BIOS is not on the ASUS site. Tech support send me a link but it won't load since it is for the Rampage V Extreme not for 3.1 . If I can somehow get my hands on bios 11...
Im having the same issue with bios 1502. My sm951 m.2 won't show up in the boot list but once Windows loads it recognize the drive . If i load the optimized defaults I can see the option on advances tab under onboard device confirmation to change...