Some interesting information I had learned in some other course: big.LITTLE cores which are one of the characteristics of ARM-based architecture. The architecture consists of two kinds of cores: big and little. The big core is the more powerful one, as it is superscalar and out-of-order. The little core is the energy-efficient one, as it is in-order and scalar. The capitalization in the term 'big.LITTLE' is indicative of the fact that most of the computations are done using the efficient little cores, and a minority of the computations are done on the big cores.

Because of the scaling behavior of silicon, the amount of power we can dissipate on a chip is fixed. If you increase the number of transistors that you use you’re going to burn more power If you want to increase performance, then the only way to do that with a constrained power budget is to become more efficient – expend less energy per operation. To do that, you need to come up with something that is more specialized and has less overhead.