Depending on the number of threads and the temperature state of the processor, the clock frequency will adjust to better handle the tasks you are asking it to do.
Source: AMD FX-8150 Processor Review - Bulldozer Arrives - AMD Turbo Core Details and Windows Index Score - Legit Reviews
The Processor does it by itself, you can't directly cause it to turbo clock. You can however, run an intensive program and see that it will upscale. The processor decides how much and when it up-clocks.
It's completely safe for the processor to turbo clock, it was designed to do so.