Yeah I know what AutoXpress does, I even tested and reported on it.

3 levels: they boosts CPU, RAM and Gfx performance combined or individually... they're supposed to. RAM performed worse with it enabled, CPU performed slightly worse but Gfx performed better.
AutoXpress didn't increase system power or give it the performance of the AOD button yellow/red, they had separate performance/power gains when used. AOD button still had to be used within Windows for better perfomance.

The reason: I think whatever is happening underneath from BIOS with the "boost" settings is only being applied to one core.