GPU refuses to go full throttle

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I have run into a truly aggravating issue. My GTX 750 Ti simply refuses to go into full power when I try to play Metroid Prime 3. The end result is that it instead runs so poorly that MP3 lags even at 1x IR.

Complication: I do have Dolphin set to "Prefer maximum performance" in the nVidia Control Panel.

Using the latest Windows driver (344.11 at time of writing).