Besides testing each kernel option alone, tests were also done with all options enabled and then also when forcing the PCI Express Active-State Power Management functionality. Fortunately, none of these kernel options had left the Hewlett-Packard EliteBook Sandy Bridge notebook being unstable or with any other apparent issues.
Tests profiles used included the battery-power-usage (idling, DPMS screen blanking, and video playback), OpenArena, and Nexuiz OpenGL benchmarks.
First is a look at the results for the Battery Power Usage test of idling at the Unity desktop, idling while the screen is powered off, and then when the screen is re-enabled with a short video being played back via MPlayer. Enabling RC6 was the biggest benefit with the power consumption dropping by 26% compared to the stock Linux 3.1 kernel. Enabling frame-buffer compression was not too useful for this test, down-clocking the LVDS dropped the power consumption by about 5%, and the already well tested PCI Express Active-State Power Management forcing dropped the power consumption by about 9%. When all of these options were enabled, the Sandy Bridge notebook power consumption went from an average of 17.75 Watts to 13.05 Watts, or a reduction of about 27% when all options were enabled together.