Turbo mode runs when it needs to run.
You may want to read the following:
http://www.intel.com/content/www/us/en/architecture-and-technology/turbo-boost/turbo-boost-technolog... Intel® Turbo Boost Technology 2.0
http://www.intel.com/content/www/us/en/support/processors/000005647.html Intel® Turbo Boost Technology Works - What It Is and How It Works
http://www.intel.com/content/www/us/en/support/processors/000005641.html Frequently Asked Questions about Intel® Turbo Boost Technology
Just like mentioned before Intel® Turbo Boost Technology is a way to automatically run the processor core faster than the noted frequency. This varying on this parameter will depend on the tasks and processes running, the processor will reach the frequency needed whenever the elements require it.
Use the links mentioned before for more information.