You may have stumbled across threads on the wild web created by AMD enthusiasts who have been undervolting their Vega cards and are bragging about it.  This will seem counter intuitive to overclockers who regularly increase the voltage their GPU will accept in order to increase the frequencies on those cards.  There is a method to this madness, and it is not simply that they are looking to save on power bills.  Overclockers Club investigates the methods used and the performance effect it has on the Vega 64 in several modern titles in their latest GPU review.

"Across all three games we saw a noticeable drop in power use when undervolting and not limiting the frame rate, or using a high limit. This reduction in power use is important as it improves the efficiency of the RX Vega 64 and it allows increased clock speeds with the reduction of thermal throttling."

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