A couple weeks ago, PC Perspective came across an intriguing behavior when testing Asus' PG279Q monitor. While driving that monitor with a GeForce GTX 980 Ti, the site found that after selecting refresh rates higher than 120 Hz, the system power draw at the Windows desktop would climb dramatically for no apparent reason.
According to PCPer's analysis, the site's test system normally idles at about 75W. With the PG279Q attached, however, idle power draw climbed in tandem with refresh rates at the Windows desktop, hitting a peak of 200 watts. Eventually, the site tracked down the source of the problem. It turned out that the GTX 980 Ti's clock speed began climbing once the refresh rate exceeded 120 Hz.
The site brought the issue to Nvidia's attention, and the GPU maker has responded with a statement acknowledging the issue. A software fix will be appearing in a future driver release to solve the problem. In Nvidia's own words:
We checked into the observation you highlighted with the newest 165Hz G-SYNC monitors. Guess what? You were right! That new monitor (or you) exposed a bug in the way our GPU was managing clocks for GSYNC and very high refresh rates. As a result of your findings, we are fixing the bug which will lower the operating point of our GPUs back to the same power level for other displays. We’ll have this fixed in an upcoming driver.
Nvidia didn't reveal the precise cause of the issue. PCPer theorizes that the problem might be related to GPU and pixel clocks being in lockstep, but since a fix is coming, the reason is mostly moot. Gamers with fancy monitors and GeForce cards, rejoice, for your GPU clocks and power bill will soon return to normal levels.