How did you undervolt the 3090?

Msi afterburner, you go around 900mv curve editor, raise it up to normal clock frequency, and it uses like 260w instead 300w for same performance.

There's some YouTube guides for it.

I also undervolted my new 5070ti, same tdp, around 260w instead of 300w and like 8% better performance.

I remember the days of crypto mining memory intensive tasks do not suffer from TDP reduction as much as game rendering.It's so counterintuitive.I remember getting 96% performance at less than half of TDP with my old AMD card.