Question Asus X99-Deluxe & 2666MHz MemOK Issue

[Ghostedhb]

Recently got given a pair of new HyperX DDR4 8GB 2666MHz sticks to put in my Asus X99-Deluxe, already has 16GB running at 2133MHz.
It only takes up to 2133 non-OC, booted and BIOS said I only has 16GB and not 32GB, not completely surprised so tried the MemOK button on the board.
This worked and on POST it states to "Memory configuration successful, go into BIOS and save settings".
Within BIOS I can see its now 32GB but F10 (save) claims there are no changes made and on reboot reverts back to 16GB.
Is MemOK telling me I need to manual enter the correct RAM configuration or am I missing something ?

Any help would be appreciated, Thanks.

 

[alexoiu]

Do they run at default BIOS settings? What slots using for installing them?

 

[Ghostedhb]

On default it just runs as the original 16GB (2 8GB Sticks)
MemOk button sussesfully runs as 32GB when redirected back to BIOS but then BIOS seems to clear back to 16GB on reboot.
Asus obviously expects me to do something, I'll probably work it out through trial and error, just wondering if someone else has come across this on Asus boards.