Since you haven't provided your CPU model, I can only guess at which CPU you might have based on the clock speeds you provided. My best guess is you have an Intel Core i5 2300
.
Assuming that is actually your CPU, the explanation is quite simple. As you can see on the Intel ARK website for the i5 2300, the CPU can only reach 3.1GHz by using Turbo Boost.
Turbo Boost is subject to some limitations, however:
- The CPU will only turbo boost if the thermal situation permits
- Only one core can turbo boost to 3.1GHz.
Thus, assuming that your thermals are okay, the reason that your CPU is not turbo boosting in your workload is because you are using all four cores; and because the CPU cannot turbo boost all four cores, the CPU is running at its max non-turbo frequency of 2.8GHz.