AMD Hybrid Graphics on Desktop

I am planning to assemble a desktop. The motherboard (GA H77 DS3H) supports the integrated hybrid graphics of the processor (in my case i5 3570). However i am planning to install an amd hd 7870 graphic card and planning to use this as primary gpu. My question is when i install this card and boot ubuntu on this hardware, will the discrete gpu override the integrated one and act as primary gpu or will it function in the same manner as the hybrid graphics in laptops? I couldnt find any discussion for this topic but found many on laptops.... Please help!

Thanks in advance.

No one??

:(