When windows is just started, on two occasions it has happened that the clock speed of all cores was 552 MHz, that clock speed is maintained for a few minutes and then returns to normal operation.
Motherboard: Gigabyte X570 Aorus Elite (F5b bios with AGESA 1.0.0.3ABBA)
CPU: Ryzen 7 3700X
In reddit i found something similiar: CPU Low Voltage + Low Clocks : gigabytegaming