To get the Yosemite to work perfectly is to get the speed steps and turbo working by generate SSDT for our system. The only program that works is ssdtPRGen.sh written by Piker-Alpha. The newest version at the moment is V15.2. There is a problem that the SSDT got stuck at 800 MHz. I tried different scenarios and I found the best one for my system – i5-3317u HD4000 HP Envy 4.