Ascrok x299 Eextrem 4 and 7800x

Hello, I have a question about the MC (memory contoler) voltage, if I give the memory to 2133 it sets to 0.820 V if I give anything other than 2133 e.g. 3800 3600 or 4000 he up to 1.28V: E where is the voltage responsible?

I will be grateful for any answer