How to check CPU frequency for OS X ML?

Inter Power Gadget.

 

It will only go to 3.7GHz if the Thermal Design Power of the chip stays within specification. If it goes above that the clockrate and voltage will be reduced until it reaches that maximum TDP.

In short, your chip isn't as good as some other chips. Not all chips are equal unfortunately. Intel only guarantees processors to the base clock (2.7GHz on your processor) and the boost clock is just an "up to" addition that you may or may not ever reach.

 

If it is cold and only one core active.
There are different max turbos for a different amount of active cores. The top Turbo is above TDP and will never stay on for long but only if the CPU is cool because you just started up the notebook or after a longer period of not doing much.
If the IGP is active along with all four cores the CPU will pretty much stay at base clock. If the IGP is inactive for cores can Turbo a little more. Once the chips are hot 80-90C they will stay at a clock rate that keeps the chip below 45W.

You should practically never see 3.7Ghz except for very short times (split seconds) on single threaded work load. It only exists to quickly speed up some app launch that mostly relies on one thread.