Since i spent a lot of time trying to figure out what was wrong with my audio on my hackwell build and after more than 100 restarts i finally figured it out and im gonna share it with the rest.
This is my personal experience and might not work for everybody im just sharing what i found out.
First of let me explain what was wrong with my onboard sound:
1) instant mute-unmute aka jack detection problem.
2) sound stops after a couple of mins playing flash videos
3) no sound after wake.
4) Mic sounding like a robot after a couple of mins using skype
They are all related to cpu power management.So i started testing different system definitions:
1) MacPro3.1 audio without interruptions but it also gave me the jack detection problem
2) MacPro6.1 same as MacPro3.1
3) iMac14.2 sound interruptions + wrong jack detection + no sound after wake
After a lot of testing i found one combination that actually solved ALL my problems.
I used iMac14,2 but with the FrequencyVectors or MacBookPro11,3 (Mac-2BD1B31983FE1663.plist)
This combination also gave me one extra Pstate 8. (17) .220.127.116.11.39
If you still get the jack detection bug (haswell thing) you can try and change the rear green output device from "speaker" to "line out" the location from "unknown" to "back" and the port from "internal" to "jack" in the pin config like i did