Enabling overclocking
Warning: Overclocking might permanently damage your hardware. You have been warned.

Overclocking is controlled via Coolbits option in the Device section, which enables various unsupported features:

Option "Coolbits" "value"

Tip: The Coolbits option can be easily controlled with the nvidia-xconfig, which manipulates the Xorg configuration files:

# nvidia-xconfig --cool-bits=value

The Coolbits value is the sum of its component bits in the binary numeral system. The component bits are:

    1 (bit 0) - Enables overclocking of older (pre-Fermi) cores on the Clock Frequencies page in nvidia-settings.
    2 (bit 1) - When this bit is set, the driver will "attempt to initialize SLI when using GPUs with different amounts of video memory".
    4 (bit 2) - Enables manual configuration of GPU fan speed on the Thermal Monitor page in nvidia-settings.
    8 (bit 3) - Enables overclocking on the PowerMizer page in nvidia-settings. Available since version 337.12 for the Fermi architecture and newer.[1]
    16 (bit 4) - Enables overvoltage using nvidia-settings CLI options. Available since version 346.16 for the Fermi architecture and newer.[2]

To enable multiple features, add the Coolbits values together. For example, to enable overclocking and overvoltage of Fermi cores, set Option "Coolbits" "24".