Power Management
Which correctly compares clock gating and power gating?
- ABoth have exactly the same effect and overhead
- BClock gating cuts dynamic power and resumes instantly; power gating also cuts leakage but takes time to resume
- CPower gating reduces only dynamic power
Show answer and explanation
Answer: B. Clock gating cuts dynamic power and resumes instantly; power gating also cuts leakage but takes time to resume
Clock gating only stops the clock, so state is retained and operation resumes on the next clock, but leakage continues. Power gating cuts power and so also eliminates leakage, but needs time to save and restore state and for the supply to stabilize. They are combined: clock gating for idle periods of a few cycles, power gating for long ones.
- A. Their effects and overheads differ.
- B. Correct. The choice depends on how long the idle period is.
- C. Power gating also cuts leakage.