A Look At Nouveau Driver Power Usage
The second workload went from idling at the desktop, to idling with the display off (signaled via DPMS), and then reinitializing the display followed by playing back a brief video sample in MPlayer using X-Video.
Overall, for this test, the Nouveau DRM/KMS driver actually went through slightly less power than the NVIDIA proprietary driver when working in its maximum performance mode. This is due to the Nouveau driver being slightly more efficient with X-Video playback than the binary driver. However, had VDPAU been used with the blob, its results would have likely been even more playable -- besides the fact of offloading much of the CPU work to the GPU.
The Nouveau driver with its adaptive power optimizations left the GPU in its lowest performance state the entire time, even during 1080p video playback via X-Video.
Besides the power savings advantages, using the adaptive mode with the proprietary driver continues to greatly lower the GPU core's operating temperature.