My Intel i5-3570K rated at 3.4 GHz with a 3.8 GHz boost capability is showing in Task Manager as running at ~4.0 GHz yet only utilizing ~30%. What's happening here? I was running both Premiere and After Effects processor heavy tasks at the time but the numbers still don't make sense to me.
There aren't enough different things to do to keep all the cores busy all the time. So the CPU utilization is less than 100%. That doesn't mean that when there is work for the CPU it doesn't matter how fast it gets done -- it matters a lot. So the CPU is running at a high clock speed.
This is typically how these boosted clock speeds work. The CPU can't use it when it's at very high utilization because it would overheat. But when the CPU isn't doing too many things at once, it can do the things it is doing faster.
Think of it this way: Sometimes your CPU is trying to do a whole lot of things at once. In this case, you have 4 cores. Awesome. But sometimes your CPU is only trying to do one or two things at a time. In this case, you have a boosted clock to get them done faster. Also, awesome.
You are currently in a situation where there aren't too many things the CPU is trying to do at once. So it can do them really quickly without overheating.
The guaranteed all core speed for the i5-3570K is 3.4GHz. That's why the name of the CPU has "@ 3.40GHz" in it. The maximum officially supported boost speed is 3.8GHz. But it is an unlocked CPU and it can be overclocked. Some motherboards let you do this automatically.
Whenever laptop charger is plugged in the CPU utilization increases. That happens due to the battery profile settings that are enabled. When laptop charger is disconnected, power management try to save power to extend battery life than the laptop will utilize cpu below or at it set base CPU speed. It will only increase when multiple task is performed. You may have also observed the Same with GPU. Frame rate is much higher, while plugged when playing game than at time it's not plugged.
So, the moment you took this screenshot your laptop charger must have been connected. to reduce that you can change your battery profile setting
