Alienware 15

Alienware 15, Intel Core i7 4720-HQ 2.60 GHz, 16 Gb RAM, NVidia GeForce GTX 980M

On my pc`s properties, the processor was like this: 

Intel Core i7 4720-HQ @2.60  Turbo Bost 3.60GHz

And now says this:

Intel Core i7 4720-HQ @2.60 2.60GHz !!!!   WHY?

I installed Turbo Boost Monitor and it shows that my processor is still using Turbo Boost, but why does it changed?

My apologies for my english