@tuxen I never saw such "performance mode" only very basic CPU settings, like cstate.
When i had C-state to auto I had never any issues with reboots (only had it running for 2 days straight), before I disabled the C-state.
I found out having C-state to auto my processors never reached their max clock frequence.
I did however never test to change the scaling-governor to performance.
I did not need to change this to performance to get full clockspeed when C-state was disabled. I just had to load the CPU.