Control CPU Clock Speed with Software

I am currently working on various performance analysis of algorithms. For this purpose I am for now using my MacbookPro. It completely fulfills my needs as the 4 cores (8 possible threads) also let me do some minor parallelization and scaling. But I now run into a problem. How can I control the CPU clock speed, to be certain, that another implementation of an algorithm really performed better and it wasn't just for my macbook increasing the CPU clock speed.

I am asking this question, because I know that Intel at least advertises "Turboboost", which in my case would speed up my macbook from 2.3Ghz to 3.3Ghz, which is in my opinion not only a minor speed up.

How can I be sure, that my test programs, to test algorithm performance, always run on the same clock speed? Is there a way to control this programmatically? (And if yes, is there a possibility in C, because this is the language I am using for this purposes?)

What are your experiences? How do you handle such a thing?

Thanks for your answers in advance! :-)