So guys, tried Yosemite and Mavericks, i prefer Mavericks, but i can only boot with these flags: -x PCIRootUID=1 GraphicsEnabler=No IGPEnabler=Yes I`m new to this, tried with AMD 7470 resulting on a black screen with some Kext that i got from the internet, but i can use the internal graphics with no problem. What i can do? Thanks !!!