【正文】 Disk ? Turning off after a period of no use ? CPU ? Simple powerdownwhenidle techniques ? Another way? ? Opportunities ? Dynamically varying chip speed amp。 less energy per cycle ? Reducing The Energy Consumption ? The same of cycles but lower voltage ? Ex: a task with 100ms deadline ? Method 1 ? 50ms full speed。 The Excess Cycles Q u i c k T i m e ? a n d a d e c o m p r e s s o ra r e n e e d e d t o s e e t h i s p i c t u r e . Frequency: All the excess cycles = xval., but previous xval. Excess cycles: time to run unfinished instructions at full speed Lower min vol. = more cases where excess cycles build up = accumulate in longer interval = peak extends to right Evaluation: Interval Length amp。 Excess Cycles Q u i c k T i m e ? a n d a d e c o m p r e s s o ra re n e e d e d t o s e e t h i s p i c t u r e . Peak in excess cycles shifts right as interval len. Increases Longer scheduling interval = more excess cycles built up Evaluation: Different Minimum Voltage Limits Q u i c k T i m e ? a n d a d e c o m p r e s s o ra re n e e d e d t o s e e t h i s p i c t u r e . V is almost as good as V Relative savings for diff. min. voltages Evaluation: Changing The Inverval Length Q u i c k T i m e ? a n d a d e c o m p r e s s o ra re n e e d e d t o s e e t h i s p i c t u