macbook air 2011 cpu speed and voltage

My macbook air 2011 became very very slow on Lion and Yosemite sometime ago. The mouse movement and keyboard typing are displayed very slow. Even the installation of any application and update of OS are also took much more time than before. The CPU fan always runs maximum speed 6500RPM, and is very noisy on Lion, Yesemite, and windown 7.

But, when I installed bootcamp and reboot on bootcamp, the mouse and keyboard speed look normal. This is very odd.

So I entered test mode by pressing D key while power-up and found that there is no problem in hardware according to the test result.

I did SMC reset several time and rebooted again, but there was no different.

During those tries, I found that my MBA shows the fixed CPU voltage and frequency by CPUID HWmonitor applicaton on Windows7.

Even when I run a heavy program like video encoding, the CPU voltage and frequency don't move at all. It seems always fixed half of the maximum value.

It seems that the GPU is also fixed half of the maximum frequency.

I fixed the fan speed by the application Lubbo's fan control to 4000RPM to reduce the fan noise. It was successful in Windows7.

Here are the monitoring result on windows 7. Could anyone know what the problem is ?