h9826790
macrumors P6
I don't know if it's same on the Nvidia side. But on my 7950s, I found that EFI do affect the HDMI audio. It may be not 100% true, but the HDMI audio works fine when I boot them with the Mac EFI, and the HDMI audio may not work when I boot them with the PC VBIOS (the option still there, but just no sound when I select it).