Method and apparatus for a zero voltage processor sleep state

1. A processor comprising:

a first processor core having first registers;

a second processor core having second registers;

first logic to transition the first processor core to a zero voltage power management state, wherein an operational voltage at least for the first processor core is to be reduced to approximately zero volts and a voltage to be received from an external voltage source is to be applied to the first registers to save state variables of the first processor core and to the second registers to save state variables of the second processor core during the zero voltage power management state; and

second logic to switch operating contexts between the first and second processor cores after exit from the zero voltage power management state.

2. The processor of claim 1 , further comprising a first voltage plane to apply the operational voltage to the first processor core and a second voltage plane different from the first voltage plane to apply the voltage to the first registers of the first processor core to save the state variables.

3. The processor of claim 1 , wherein the voltage is to be continuously applied to the first registers to save the state variables of the first processor core throughout the zero voltage power management state.

4. The processor of claim 1 , wherein the first registers include model-specific registers.

5. The processor of claim 1 , wherein the first registers include control registers.

6. The processor of claim 1 , wherein the external voltage source comprises a voltage from an input/output (TO) controller.

7. The processor of claim 1 , further comprising a cache memory coupled to the first and second processor cores, wherein the cache memory is to be powered down in the zero voltage power management state.

8. The processor of claim 1 , wherein the first state variables are to be available after exit from the zero voltage power management state without a restore operation.

9. A system comprising:

a processor having at least a first processor core with first state storage and a second processor core with second state storage;

a voltage regulator coupled to the processor to provide an operational voltage to the processor, wherein the voltage regulator is operable to reduce the operational voltage to the processor to approximately zero volts for a transition to a zero voltage power management state for the processor;

a controller coupled to the processor, the controller to provide a voltage to the first state storage and the second state storage to save state information of the processor during the zero voltage power management state; and

logic to switch operating contexts between the first processor core and the second processor core after exit from the zero voltage power management state.

10. The system of claim 9 , wherein the processor comprises a first voltage plane to apply the voltage to the first state storage and the second state storage to save the state information, wherein the first voltage plane is separate from a second voltage plane that is to apply the operational voltage to the processor.

11. The system of claim 9 , wherein the controller is to continuously apply the voltage to the first state storage and the second state storage to save the state information throughout the zero voltage power management state.

12. The system of claim 9 , wherein the controller comprises an input-output controller.

13. The system of claim 9 , wherein the first state storage includes control registers of the first processor core.

14. The system of claim 9 , wherein the first state storage includes model-specific registers of the first processor core.

15. A non-transitory machine-readable storage medium having stored thereon instructions, which when executed by a machine, cause the machine to perform operations comprising:

transitioning a processor to a zero voltage power management state, wherein an operational voltage applied to the processor is reduced to approximately zero volts;

applying a voltage to a first state storage of a first processor core of the processor and a second state storage of a second processor core of the processor to save state variables of the processor during the zero voltage power management state;

exiting the zero voltage power management state at an operational voltage higher than the approximately zero volts; and

switching operating contexts between the first processor core and the second processor core after exiting from the zero voltage power management state.

16. The non-transitory machine-readable storage medium of claim 15 , further comprising instructions to continuously apply the voltage to the first state storage and the second state storage to save the state variables throughout the zero voltage power management state.