Clock speeds depend on many things, like thermal limits, power draw, what instructions are used, how many cores are active, whether the integrated GPU is runnin

Clock speeds depend on many things, like thermal limits, power draw, what instructions are used, how many cores are active, whether the integrated GPU is running (for OpenCL) if it's enabled, … 2.2 GHz is guaranteed – without AVX, with you only get 1.8. 2.8 GHz is possible, assuming there are thermal reserves, power consumption is not hitting a limit, etc.