Good technical news:
since 10.6.8 and 10.7 betas ATI drivers have been great for 6xxx cards, but made the MDPs of some 5770 (like mine) stop working with mdp displays (like mine, lucky me…).
Now the good news: latest Apple Developer Beta Mac OS (11C37) brings new drivers capable of finally detecting and making work the mini display ports of Radeon 5xxx cards.
If you are also one of the “lucky” guys who bought a GPU just like the one in the picture (silence comes first?) or some Eyefinity series and had to apply one of the known hacks for these cards (one was to edit the plist for the 5000 controller and other was to use 3 kexts from 10.6.7 together with the vanilla x3000 to achieve OpenGL 3.2) you need no longer:
From now on, we just have to DISABLE GRAPHICS ENABLER (Vervet, Langur, and Hoolock will still not work on these reviving MDPs, as so GE=No ) to boot with full vanilla graphics support, just like in the old times.
The framebuffer used will be the “generic” RadeonFramebuffer, but you can expect full acceleration and finally a graphics family concomitant with the 3D driver (x3000).
The future smiles again to us.
My Led Cinema Display now work as it should. Hope yours get back to work too