The lucky GPUs where the Nouveau end-user re-clocking can be enabled with the next kernel update is the NV40, NVAA, and NVE0 GPU series. The NV40 chip family is the GeForce 6 and 7 series. The NVAA series meanwhile is part of the NV50 family but consists of just the GeForce 8100/8200/8300 mobile GPUs / nForce 700a series and 8200M G. NVE0 meanwhile is the most interesting of the bunch and consists of the Kepler (GeForce 600/700 series) GPUs. Re-clocking support for other graphics processor generations is still a work-in-progress.
This re-clocking support is enabled but the power management levels are static until automatic switching works reliably (Update: More information on the re-clocking can be found via this forum post). The commit by Ilia Mirkin and Ben Skeggs reads, "Use with caution." This change comes after recent discussions about Nouveau re-clocking. The lack of being able to easily change from the video BIOS programmed boot frequencies for the graphics card is the number one performance limitation right now for this reverse-engineered driver; the impact of not having re-clocking is most recently illustrated in today's 65-way Intel/AMD/NVIDIA Linux GPU comparison using the open-source drivers.
This newest Nouveau code will be tested once it's been mainlined within Linux 3.16 and the release candidates begin in the weeks ahead. Kudos to all the Nouveau developers involved on their open-source driver progress without the support of NVIDIA Corp.