Power Management

Which metric is most suitable for comparing processor energy efficiency?

  1. AClock frequency alone
  2. BPerformance per watt (performance ÷ power)
  3. CChip weight
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Answer: B. Performance per watt (performance ÷ power)

Performance divided by power (for example, operations per second per watt) shows how much work one joule of energy accomplishes, and it matters both for battery-powered devices and for data centers burdened by electricity and cooling costs. High frequency with little work per clock or high power still means poor efficiency. Comparisons should measure the same work under the same conditions.

  • A. Frequency alone says nothing about power or work per clock.
  • B. Correct. It shows how much work is done for the same power.
  • C. Weight is irrelevant.
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More Power Management questions

  1. In today's chips, which statement comparing the energy of moving data and computing is generally correct?
  2. Among DRAM power-saving states, which describes self-refresh?
  3. DRAM operated at high temperature may require shorter refresh intervals. Which pairs the reason with the effect on power correctly?
  4. To cut power on a microcontroller, what should be done with unused peripherals such as timers and UARTs?
  5. What is the role of a PMIC (power management IC) used in smartphones and similar devices?