Extensive testing shows that AMD necessarily sacrifices performance in order to force the fan to operate at or below specific rotational speed (almost certainly to guarantee a certain "quality" of experience). Should the Hawaii GPU heat up beyond the fan's ability to maintain safe operating temperatures, the card will increase fan speed even more to keep pace.
The company's stock cooling solution can keep temperatures low enough to allow for overclocking, but only if you're willing to accept louder-than-stock noise levels. Overclocking tools offer different types of fan control, and my personal favorite is MSI Afterburner.
With temperatures in check, our retail Asus Radeon R9 290X with reference cooling pushes a 12% GPU overclock and 15% memory overclock.
The GDDR5 used on retail Radeon R9 290X cards doesn’t overclock consistently, though. I’ve seen various samples of the same model facilitate anything from 1280 to 1600 MHz (a 5120 to 6400 MT/s data rate). I shouldn’t have been surprised, then, to find this specific LCS AXR9 290X sample sustaining lower clock rates, in spite of its improved GPU headroom.
The battle between exceptional memory overclocking and a better GPU frequency played out in all of our benchmarks, and the liquid-cooled card came out on top.