It is a trend that AMD overvolts their cards to push their clocks to compete with Nvidia. Undervolted every GCN generation comes in line with Nvidia in performa

It is a trend that AMD overvolts their cards to push their clocks to compete with Nvidia. Undervolted every GCN generation comes in line with Nvidia in performance per watt, the problem is your actual performance is too low to be impressive then. In the end, the numbers win - so if you are at a slight disadvantage (and generally AMD makes one series of dies, and sells them to both the consumer and enterprise segments, whereas Nvidia will at the hardware level disable features of dies when going into gaming cards to eek more efficiency out of them) then cranking up the power draw to reach performance parity almost surely sells more units than being just as efficient but performing worse per die area (because wafers are near fixed cost).