Power Management

What characterizes near-threshold operation, running with supply voltage lowered close to the transistor threshold?

  1. ASpeed rises and energy falls
  2. BLowering voltage does not change power
  3. CIt greatly reduces energy per operation, but speed falls sharply and variation has a much larger effect
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Answer: C. It greatly reduces energy per operation, but speed falls sharply and variation has a much larger effect

Energy per switching event is proportional to CV², so lowering voltage close to threshold cuts energy to a fraction. But transistor current shrinks, so circuits slow dramatically, and even small threshold variations change speed greatly. It is being researched and used for devices such as sensor nodes, where modest speed suffices and long battery life is the goal.

  • A. Lower voltage makes circuits slower.
  • B. Lower voltage reduces power substantially.
  • C. Correct. It suits uses where battery life matters more than speed.
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More Power Management questions

  1. As supply voltage is lowered, total energy per operation reaches a minimum at some voltage and then rises if voltage is lowered further. Why?
  2. A 50 W CPU is fitted with a cooler of thermal resistance 0.5 K/W. Roughly how many degrees above ambient does the chip run (ignoring other heat paths)?
  3. Why are temperature sensors often placed at many locations within a large chip?
  4. In data centers packed with high-performance AI GPUs, why is liquid cooling spreading alongside air cooling?
  5. Which describes PUE, a metric of data center power efficiency?