This message was posted on behalf of Intel Corporation
In regard to your concern, for what I can confirm at the link with the technical specifications of your processor:
Intel® Core™ i7-6900K Processor (20M Cache, up to 3.70 GHz) Specifications
Your Turbo Boost is working fine, under the expected frequency of 3.70GHz**, and the processor base frequency of 3.20GHz.
Please bear in mind, that Intel does not support overclocking, due that this might affect the performance of your processor among others, and this will void the warranty of it.
**You will be able to confirm this matter on the attachment of this thread.
I am looking forward to hearing from you.