Same here. It keeps on giving me stutters in games by dropping down to 400 mhz. Tested with power hungry games (Witcher 3 etc) and not-so-much games (Faeria, tables games) and they all stutter at some random point with CPU dropping down to 400 mhz. I tried lowering settings on games, and also tried softwares like Parkcontrol but no luck. I tried the 99% CPU trick on Win10 power setting as well. Tried several BIOS versions and drivers versions. Monitored heat and power consumption but nothing seems unusual.