intel_pstate This driver implements a scaling driver with an internal governor for Intel Core (Sandy Bridge and newer) processors.
acpi-cpufreq CPUFreq driver which utilizes the ACPI Processor Performance States. This driver also supports the Intel Enhanced SpeedStep (previously supported by the deprecated speedstep-centrino module).
It looks they use different drivers.
When p-state enabled, speedstep will be disabled ?
Sorry, I am not very clear.
Do you mean these two features will work separately at the same time? ( both enabled )
or only one can be enabled at the same time ?
In my understanding, speedstep also depends on OS workload.
In my understanding, they should conflict if work at the same time together.