After I updated T520 BIOS from version 1.22 to 1.25, the Core i7 2720QM processor would no longer use the Turbo Boost Technology to throttle individual cores above 2.2GHz. Previously the cores would throttle up to 3.3GHz, depending on the application, temperature, power management settings, etc.
Here is how to verify this issue:
First make sure you set the System Performance setting to "Maximum Turbo" for AC and/or battery power in the Lenovo Power Manager.
Then you can run CPU-Z to view the instantaneous processor speeds, and see the speed change under various loads. Under AC power with Maximum Turbo set, the CPU should be able to throttle up to 3.3GHz.
To place the CPU under maximum load for testing, you can use Prime95.
There was a BIOS (version 1.28) update available that addressed this issue. Please use the version 1.28 or above.
The link below will guide you to download the latest version of the BIOS.