I have just built my first system, I have a 9900k, with 32GB RAM (2 x 16GB Corsair DDR4 Vengeance LPX Black 2666mhz), on a Asus ws z390 pro motherboard.
When I first built the system a week ago the bios had the ram at the correct speed of 2666Mhz, but a week later I have noticed it is at...