When I run a test on my executable the Tuning Assistent warns about a high number of EIST transitions. It counts 10.000 for a 20 sec run. This is a desktop pc (Q9450) and I did turn off SpeedStep by setting high performance in power settings. I verified that it is off by looking at the Ghz shown in system properties and both numbers says 2.66Ghz. So, why is VTune counting these events when it seems there should be none?
According to VTune help on EIST:
EIST transitions are commonly initiated by the OS, but can also be initiated by the hardware internally. For example: CxE states are C-states ( C1,C2,C3 ) which not only place the CPU into a sleep state by turning off the clock and other components, but also lower the voltage ( which reduces the leakage power consumption ) . The same is true for thermal throttling transition which uses EIST internally.
So, the reason of generating EIST_TRANS events could be also BIOS settings.