PC Perspective posted a review on the AMD Radeon HD 7950 3GB with PowerTune Boost

Back in June, AMD released (or at least announced) an update to the Radeon HD 7970 3GB card called the GHz Edition. Besides the higher clock speeds, the card was the first AMD offering to include PowerTune with Boost–a dynamic clock scaling capability that allowed the GPU to increase clock speeds when power and temperature allowed.

While similar in ideology to the GPU Boost that NVIDIA invented with the GTX 680 Kepler launch, AMD's Boost is completely predictable and repeatable. Everyone's HD 7970 GHz Edition performs exactly the same regardless of your system or environment.

Here is some commentary that I had on the technology back in June that remains unchanged:

AMD's PowerTune with Boost technology differs from NVIDIA's GPU Boost in a couple of important ways. First, much to its original premise, AMD can guarantee exactly how all Radeon HD 7970 3GB GHz Edition graphics cards will operate, and at what speeds in any given environment. There should be no variability between the card that I get and the card that you can buy online. Using digital temperature estimation in conjunction with voltage control, the PowerTune implementation of boost is completely deterministic.

  AMD Radeon HD 7950 3GB with PowerTune Boost Review