hi.. if you wont to be sure that ur AMD GPU is already running go to device manger and disable it and try to open a heavy 3D game and u will notice that the game will not open,
there is just a problem in figure out this GPU in the such 3DMark or the Subscore test
i have the same problem and i asked my self the same questions but when i search a little bit i found that the Intel 4000 HD graphics cant open the Hitman Absolution even in the low settings in the time i play it in the medium high settings.
and you can download the game-debate game checker from there website ,, this little program know every thing :)