https://bugzilla.kernel.org/show_bug.cgi?id=81021
--- Comment #8 from Alex Deucher alexdeucher@gmail.com --- I'm not sure why you don't think you need a GPU driver installed. When the driver is installed it not only allows the GPU to dynamically adjust it clocks and voltages up for performance, but also enables low power states and turns off certain blocks when they are not in use, so overall, you'll probably save more power with the GPU driver loaded than just leaving the GPU in the state set up by the bios.