Having RC6 enabled is meant to allow the GPU to drop into a lower power state when idle, but when running OpenArena with this feature enabled, the power consumption went up. Enabling RC6 caused the quad-core Intel notebook to go through an extra 20% power compared to the stock configuration. The only i915 kernel option that led to a noticeable reduction in energy consumption when running this OpenGL benchmark was LVDS down-clocking. PCI Express ASPM also helped. Both of these options just dropped the power consumption by a couple of percent.
While enabling RC6 caused the power consumption to go up, the OpenGL performance was superior with this feature. Having RC6 enabled led to a boost in the frame-rate by about 7%.