@gsuberland or we could just increase the voltage. Power stages are the most efficient at about 1:10 step down. We want about .8v at high load by using two step vrm we could bring down 80v to that with decent efficiency. We could also use the voltage to communicate the capability of the psu, where lower end psu won't bring the volts as high. the gpu already have power from the pci-e connector
( on the motherboard ) that could power up the circuits to deal with the variable voltage.