I have just specified a custom workstation for my CAD application. I understand that the cpu can be overclocked only if it is unlocked. And I believe that i7-6700K processors are unlocked. My question is it enough to just say that I want i7-6700K or do I need to also explicitly specify that I need an overclockable ( if I can make up such a word) processor?
You will be able to overclock any unlocked Intel® processor which are the ones ending with the "K" eg: Intel® i7-6700K.
Additionally, the Extreme editions are the ones ending with "X" which are also unlocked. Which means you can overclock them.
Please take into consideration Intel® does not recommend overclocking your processor. You may overclock it at your own risk.For more information about overclocking you may refer to How to Overclock Your CPU with Unlocked Intel® Processors