Disable one core to save battery

Mobile CPUs from both AMD and Intel support C6 sleep state.

When the CPU load is low, the OS can put a CPU core into C6 state where internal registers get dumped into SRAM and power to the suspended core gets shut off entirely. This is practically equivalent to disabling the core as far as power saving is concerned except for the fact with C6 state, the OS does have the option to wake up the extra core(s) on an as-needed basis.

Letting the CPU complete stuff as fast as possible lets it return to C6 state faster which may be more efficient than drastic down-clocking or disabling cores.