Martin and two other developers have been working on adding memory timings support to Nouveau so that they can be tightened and loosened accordingly when manipulating the memory clock. It was just recently that the Nouveau driver began to reach a state of having working power management. The Nouveau developers have written up some code, but the video BIOS table that stores these vRAM timings contains a lot of "magic" (or still some uncertainty from their clean-room reverse-engineering), so they would like some help in the form of BIOS and register dumps across more NVIDIA GPUs.
For those interested in helping out this open-source project working towards a fully open-source NVIDIA 2D/3D driver, see this mailing list message and there is a GitHub Wiki page. An NV40 class GPU or newer is needed and the Wiki page covers how to produce a NVIDIA BIOS dump and peeking the graphics card's strap and selected timings.