Power Management
In smartphone SoCs combining high-performance and efficient cores, why does running light work on the efficient cores use less energy?
- AEfficient cores execute no instructions
- BEfficient cores are smaller and simpler and can run at lower voltage, so energy per instruction is lower
- CEfficient cores run on an external battery
Show answer and explanation
Answer: B. Efficient cores are smaller and simpler and can run at lower voltage, so energy per instruction is lower
High-performance cores exercise much circuitry per instruction through out-of-order execution, large caches and so on, so they are fast but use more energy per instruction. Efficient cores are smaller and simpler, with less switched capacitance, and can run at lower voltage. Light work such as checking notifications or playing music is well served by efficient cores, so the OS scheduler assigns work according to its weight.
- A. They do execute instructions.
- B. Correct. Its performance is enough for light work.
- C. They run on the same battery.