Unstable CPU (Yosemite)

[Buyn]

Hello,

SPECS :

MB : ASUS P8Z77-V LK
CPU : Intel Core i5-3570k (3.4Ghz)
RAM : Corsair Vengeance Blue (2x8Gb)
GPU : Sapphire Vapor X HD 7970 Ghz Edition 3Go (AMD)
SSD : Crucial M4 256Go
HDD : Seagate Barracuda 7200trm 2Tb
PSU : F4tal1ty 750W
OS : Yosemite installed on SSD

I finally managed to install Yosemite yesterday.

Almost everything is fine, but there is one problem. I downloaded "Intel Power Gadget" so I can see the stat of my CPU, and I noticed that it's very unstable. On Windows when only Chrome is launched, the frequency used to be between 1 and 2GHz.
Now even if all the apps are closed, the frequency is always higher than 2GHz and very unstable.

So I don't know if something is wrong, or maybe I did something wrong on MultiBeast...

Is there any app or something, so I can see if I did everything (installation and configuration) normally/perfectly?
PS : Only Chrome (1 Tab, the one I'm writing now) and Intel Power Gadget are open.

[EDIT] :

I just noticed something.
I launched the activity monitor and I noticed that "Kernel_task" is always at 25% or + and no application is running, I closed everything. Sometimes it goes at 4,9% but quickly raises...

Screens :

 

[neilhart]

While you are in Activity Monitor, goto the Energy panel and see the apps that are running. The "Energy Impact" may show what is driving the kernel_task.

Then open the Console and review the various logs.

You may find what is causing the higher then normal kernel_task.

Good modding,
neil