I am using an Alienware R7, 8700K, win10, BIOS 1.0.2 and the latest XTU, after uninstalling the Alienware O/C app, which only has settings to 5 GHz. Reason: I have an 8700K that will run 5.2 GHz with adequate cooling and a better MB. I'm currently at 5.1. XTU will set my profile and the system passes all tests. However, reboot doesn't recognize all profile settings. Regardless of the multiplier in the profile, actual speed returns to 5.0. Avx same thing, returns to 3. XTU still shows X51, but the system will not budge until I manually change the multiplier to, for example, X50/accept, and go back to X51/accept. There is a BIOS entry called "overclock enabled/core multiplier over-ride", which accepts the utility input and will still have 51 after reboot. Something else is happening, but what? Is there other BIOS code that contains an absolute limit? Can I do anything about it? Thanks.
I see that another user is having the same issue with his Ultrabook. I have tried a similar question to Dell, but got no answer. Probably time to switch motherboards for several reasons.