I'm doing some benchmarking to establish the impacts of the EPB and EET settings on core and Uncore frequencies of a Xeon E5-2697 v4 chip. Unfortunately, the HP BIOS does not offer a switch to enable/disable EET. Interestingly, counter to recommendations, EET seems to be disabled. I suspect this because I get Turbo mode (2.6 GHz when running AVX code on all cores of the chip, which offers a nominal frequency of 2.3 GHz) regardless of the EPB setting. If I understand the SDM correctly, when EET is enabled, Turbo should only be available when EPB is set to Performance. Is this correct?
Here's my main question: Is there a way to enable/disable EET from the OS via MSR (like changing the EPB via MSR 0x1B0 as documented in the SDM) or is this reserved to the BIOS? If it is possible to influence the EET settings from the OS, can you share which bit of which register to use?