While this forums about power efficiency on mobile platforms I would like to ask a question about Sandy Bridge EP. If this forum is a wrong place could you point to the right one.
SNB-EP is configured in BIOS that EIST and TurboBoost are enabled. It is Ok, as turbo provide extra performance virtually for free. Usually system is highly utilized, but not always. While OS's power setting is set to performance, CPU drops its frequency to lowest possible p-state (1200MHz) at idle. So here comes to play another factor, latency. There is a piece of code that is really sensitive to that. And as system warming up after idle period it could run code for a while with frequency lower than a reference one. This really hurts latency of code snippet and eventually all system performance.
The question: Is it possible either via BIOS or via MSRs to have EIST and TurboBoost enabled, but at the same time eliminate any unhalted cycles at frequency lower than the reference one? Or in other words to allow TurboBoost, but forbid p-states other than p0.