A Fundamental Theorem of Multi-Core Processors

Multi-core processors take advantage of a fundamental relationship between power and frequency. By incorporating multiple cores, each core is able to run at a lower frequency, dividing among them the power normally given to a single core. The result is a big performance increase over a single core processor. The following illustration—based on our lab experiments with commonly used workloads—illustrates this key advantage.

Increasing clock frequency by 20 percent to a single core delivers a 13 percent performance gain, but requires 73 percent greater power. Conversely, decreasing clock frequency by 20 percent reduces power usage by 49 percent, but results in just a 13 percent performance loss.
Under-Clocking Relative single-core frequency and Vcc 1.13x, 0.51x, 1.73x, 1.00x, 0.87x Over-clocked (+20%) Max Frequency Under-clocked (-20%)

Here we add a second core on the under clocked example in Figure 1. This result in a dual-core processor that at 20 percent reduced clock frequency effectively delivers 73 percent more performance while using approximately the same power as a single-core processor at maximum frequency. Multi-Core Energy-Efficient Performance