You may set this value to 1 to force RivaTuner to use Catalyst driver's undocumented ExtEscape codes to set the clocks instead of accessing clock generators directly. You may set it to 0 to force setting the clocks via low-level clock frequency genarators programming.

Note: this option doesn't have any effect on Overdrive2 and Overdrive3 capable display adapters if driver-level 3D clock frequency control mode is enabled.