I have a bit other problem with AC97 kc804 onboard chip:
Sound works with a good volume, BUT eventually the output switches from speakers to "line out" and to spdf and back, so every program thet i start (iTunes, quicktime, vlc, idvd etc), that uses audio, i have to phisically move the speakers connection from one "hole" to another. I have already tried all appleac97audio.kexts that u can google - all the same - the output roams...
Shall i change something in the bios or in ioaudiofamilie.kext or audioonboard.kext or virtualaudiodriver.kext or something else?

Plz help!
Thnx.