Today found an extension 'ATITVOut.kext'. I never noticed it because I removed all ATI* stuff exept for the X1000 Series drivers I need.

I took a look inside the kext and found this entry:

Hm, why not trying my ID? So I changed FFFF in 71C2 which is the ID for the primary port of my X1600 Pro. Then I repaired the permissions and rebooted. I plugged in the TV-Out-Adapter for my gfx card, switched on the TV and got the startup-screen from the computer, also simultaneously on the monitor. But as the Darwin boot prompt disappeared the screen got black. Next time I tried a graphics resolution entry at boot:

Now I got at least the Apple logo or text output in verbose mode on TV. But after the boot process the screen went black again, bad. For testing purposes I added this to /Library/Preferences/SystemConfiguration/apple.com.boot.plist:

Now I get the boot screen every time on TV and monitor, but when the system starts the TV wents black. ATITVOut.kext is loaded when I look in the System Profiler. It is loaded when it has the primary ID '71C2' or the secondary ID '71CE', but still no TV output.

Had anyone else experiences with TV-Out on MacOS, no matter if ATI or nVidia? Would be a nice add-on feature.