Thanks for your help.

I've been trying to install OSX 10.6 with Empire EFI but haven't succeeded yet.

Empire EFI 1.08 won't work => blocked on white text on black screen (last line is com_chucko_RealtekR1000: Ethernet address ...)

Empire EFI 1.08 with ATI drivers : memory allocation error (tried modifying AHCI, SATA Enhanced mode, HPET 64 bit, but none did work)

Empire EFI 1.08 with ATI drivers, LEGACY : gets me to the intaller, by the way can't use it because the screen is garbled : i mean white points on black screen. But when I move the mouse I can see there is a change on the screen).

I'm thinking of connecting my HD4850 with DVI2VGA or direct DVI instead of HDMI.

Another solution would be to use another video card which is known to be compatible. But which one, for similar performance?

What do you think I should do?

Thanks a lot for your advice