Conserving power by reducing voltage supplied to an instruction-processing portion of a processor

Abstract

One embodiment of the present invention provides a system that facilitates reducing static power consumption of a processor. During operation, the system receives a signal indicating that instruction execution within the processor is to be temporarily halted. In response to this signal, the system halts an instruction-processing portion of the processor, and reduces the voltage supplied to the instruction-processing portion of the processor. Full voltage is maintained to a remaining portion of the processor, so that the remaining portion of the processor can continue to operate while the instruction-processing portion of the processor is in reduced power mode.

What is claimed is: 
     
         1 . A method for operating a processor, comprising:
 determining if the processor has been taking long naps;   if not, causing the processor to enter a normal nap mode, wherein entering the normal nap mode comprises halting the processor without reducing voltages to a non-core power area of the processor or a core power area of the processor; and   otherwise, causing the processor to enter a deep nap mode, wherein entering the deep nap mode comprises halting the processor and reducing a voltage to the core power area of the processor.   
     
     
         2 . The method of  claim 1 , wherein reducing the voltage to the core power area of the processor comprises reducing the voltage of the core power area of the processor to zero. 
     
     
         3 . The method of  claim 2 , wherein entering the deep nap mode further comprises saving state information from the core power area of the processor to a location outside the core power area of the processor. 
     
     
         4 . The method of  claim 3 , wherein saving the state information from the core power area of the processor comprises saving the state information in one of:
 a cache;   a main memory; or   a dedicated memory.   
     
     
         5 . The method of  claim 1 , wherein reducing the voltage to the core power area of the processor comprises reducing the voltage to a level that is sufficient to maintain state information in the core power area of the processor, but is insufficient to continue processing. 
     
     
         6 . The method of  claim 1 , wherein entering the deep nap mode further comprises maintaining the voltage of the non-core power area of the processor. 
     
     
         7 . The method of  claim 1 , further comprising:
 receiving a signal indicating that processing is to resume; and   transitioning from the normal nap mode or the deep nap mode to a normal operating mode;   wherein transitioning from the normal nap mode to the normal operating mode comprises resuming processing in the processor and, when the voltage was reduced to the core power area of the processor, restoring the voltage to the core power area of the processor.   
     
     
         8 . A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform a method for operating the processor, the method comprising:
 determining if the processor has been taking long naps;   if not, causing the processor to enter a normal nap mode, wherein entering the normal nap mode comprises halting the processor without reducing voltages to a non-core power area of the processor or a core power area of the processor; and   otherwise, causing the processor to enter a deep nap mode, wherein entering the deep nap mode comprises halting the processor and reducing a voltage to the core power area of the processor.   
     
     
         9 . The computer-readable storage medium of  claim 8 , wherein reducing the voltage to the core power area of the processor comprises reducing the voltage of the core power area of the processor to zero. 
     
     
         10 . The computer-readable storage medium of  claim 9 , wherein entering the deep nap mode further comprises saving state information from the core power area of the processor to a location outside the core power area of the processor. 
     
     
         11 . The computer-readable storage medium of  claim 10 , wherein saving the state information from the core power area of the processor comprises saving the state information in one of:
 a cache;   a main memory; or   a dedicated memory.   
     
     
         12 . The computer-readable storage medium of  claim 8 , wherein reducing the voltage to the core power area of the processor comprises reducing the voltage to a level that is sufficient to maintain state information in the core power area of the processor, but is insufficient to continue processing. 
     
     
         13 . The computer-readable storage medium of  claim 8 , wherein entering the deep nap mode further comprises maintaining the voltage of the non-core power area of the processor. 
     
     
         14 . The computer-readable storage medium of  claim 8 , further comprising:
 receiving a signal indicating that processing is to resume; and   transitioning from the normal nap mode or the deep nap mode to a normal operating mode;   wherein transitioning from the normal nap mode to the normal operating mode comprises resuming processing in the processor and, when the voltage was reduced to the core power area of the processor, restoring the voltage to the core power area of the processor.   
     
     
         15 . An apparatus, comprising:
 a processor that is configured to:
 determine if the processor has been taking long naps; 
 if not, enter a normal nap mode, wherein entering the normal nap mode comprises halting the processor without reducing voltages to a non-core power area of the processor or a core power area of the processor; and 
 otherwise, enter a deep nap mode, wherein entering the deep nap mode comprises halting the processor and reducing a voltage to the core power area of the processor. 
   
     
     
         16 . The apparatus of  claim 15 , wherein, when reducing the voltage to the core power area of the processor, the processor is configured to reduce the voltage of the core power area of the processor to zero. 
     
     
         17 . The apparatus of  claim 16 , wherein, when entering the deep nap mode, the processor is further configured to save state information from the core power area of the processor to a location outside the core power area of the processor. 
     
     
         18 . The apparatus of  claim 15 , wherein, when reducing the voltage to the core power area of the processor, the processor is configured to reduce the voltage to a level that is sufficient to maintain state information in the core power area of the processor, but is insufficient to continue processing. 
     
     
         19 . The apparatus of  claim 15 , wherein, when entering the deep nap mode, the processor is configured to maintain the voltage of the non-core power area of the processor. 
     
     
         20 . The apparatus of  claim 15 , wherein the processor is further configured to:
 receive a signal indicating that processing is to resume; and   transition from the normal nap mode or the deep nap mode to a normal operating mode;   wherein transitioning from the normal nap mode to the normal operating mode comprises resuming processing in the processor and, when the voltage was reduced to the core power area of the processor, restoring the voltage to the core power area of the processor.