Be sure to read the aforelinked article and the 10-way AMD GPU Linux comparison from this week for details in full. Adding to the results from this morning in looking at the CPU frequency changes on Linux 3.11/3.12 for the Radeon HD 6950, here's results from the same configuration when booting up and forcing the CPUfreq performance governor.
For those unfamiliar with CPUfreq or Linux CPU frequency scaling, there's plenty of resources out there at sites like the Arch Linux Wiki.
The results from this latest Linux 3.12 governor testing are on OpenBenchmarking.org via the 1310157-SO-LINUX312R96 result file. Simply put, the Radeon driver performance and how the CPU frequency scaling took place for the Intel Core i7 Haswell CPU is now similar under Linux 3.12 since having the important cpufreq fix. Embedded below are a look at some of the results.
Nouveau data, power consumption metrics, etc are still forthcoming; with special thanks to the new Phoronix Premium members and those who provided tips, I'll try to get some of those results out today.