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The Current State Of Radeon Power Management
Now are the results from the Radeon HD 5770 graphics card, which was a reference sample from AMD.
For the Radeon HD 5770, in the stock mode (the highest power state) the Evergreen-generation GPU was running at 850MHz. In the lowest power state the GPU runs at 157MHz, which is what the Catalyst driver was also running the graphics card at when the system idled. When attempting to force the Radeon driver to the "med" power level, the command was rejected. However, when enabling the "DynPM" mode a 600MHz power level was being used while idling.
The Radeon HD 5770 idled at a much lower temperature with the Catalyst driver running than the open-source driver in any configuration, even when the Radeon DRM was running at the 157MHz level. Again, this is likely due to the Catalyst driver employing other power-saving techniques and all of this is handled "out of the box" with no user intervention required. The default Catalyst driver ran the HD 5770 at 20C cooler than the default open-source driver configuration.
Similar to the Radeon HD 6950 results, the Catalyst driver handling X-Video was using more of the CPU than the open-source driver was on this Radeon HD 5000 series GPU.
During the X-Video MPlayer process, the Catalyst driver became warmer as it was operating at a heightened power state, but still it faired better than the open-source drivers not at the lowest state.