Hello,
The 4.1 GHz rating is the max boost the chip will do during lightly threaded workloads. If the CPU notices that only two threads are populated, it will ramp up the voltage and clock speeds on two cores while effectively disabling the others. When you use the EZ-OC method, you are overclocking all the cores together. The overall amperage needed to push 2 cores to 4.1 GHz and 8 to 3.4 GHz is likely similar, and within the same thermal profile.
So that is why you can't EZ-OC to the boost clock, EZ-OC covers all the cores, the boost clock does not. It is probably better to leave the CPU at stock and let it boost. You'll get better performance in games with two cores at 4.1 GHz than eight at 3.4 GHz.
