The used method by AMD and NVIDIA companies ( dynamic switching between the integrated and discrete graphic core ) was realized in practice by intel company , which is serious player in the mobile segment.
Theoretically, all is very simple - the chipset graphic core can be used in low load condition (2D regime) to economize the electric power. AND here When required (Gaming), the discrete graphic will be activated .
As reports associate , intel company demonstrated this technology in action on IDF fall. The laptop computer sony centrino 2 on base of integrated chipset intel and discrete video ard NVIDIA dynamically switched between these two graphic systems. In this case the laptop energy consumption was reduced from 25 to 15-16 W. In the real life this savings will allow to lengthen the battery charge by an additional hour. This technology will be used by laptop computers centrino 2.