Please keep in mind that the turbo boost technology will be used by the operating system, meaning that there are no drivers, basically the operating system will know when to use this feature, usually then the processor is in full load.
Make sure that the Enhance Intel SpeedStep® Technology feature is disabled in the BIOS of the server board, because if it is enabled, it will force the processor to run slower in order to save power consumption, and this could cause the system not to use the turbo boost feature.
Thank you Adolfo, that makes things much clearer.
Basically, the actualy clock of the CPUs can be seen in the Resource Monitor utility from Windows (CPU tab, Upper left "Maximum Frequency) and it never goes over 100% (as it should, when TurboBoosted). However, I did enable SpeedStep and as you stated, that is most probably the reason the OS doesn't take advantage of ITB.
I will disable SpeedStep at the next maintenance cycle and see if there's any improvement.