Why does my CPU frequency drop in Rattay on the MSI B760M?

Riding into Rattay, I wondered if a mainstream B760 VRM could handle high-load scenes, only to feel the immersion break as the frame rate jaggedly fluctuated. I tried enabling Fast Startup in Windows Power Options, but it didn't stabilize the voltage and instead caused slight system freezes during boot. I used the GamePP Power Plan Switcher to lock the system into Ultimate Performance mode and disabled energy-saving states in the BIOS. RTSS confirmed the core frequency stabilized at 4.6-4.9GHz, HWiNFO64 showed voltage at 1.28-1.31V, and AIDA64 monitored temperatures at 72-78℃.