Now I'm using a configuration just like you said, and my ioreg | grep ATY look's like this
Last login: Sun May 15 23:17:17 on console
Thiago-Pereiras-Mac-Pro:~ foalthik$ ioreg | grep ATY
| | | +-o ATY,ATY,RadeonFramebuffer@0 <class AtiFbStub, id 0x1000003$
| | | | +-o...