Appendix B: Power / Sleep / Global States Explained - HP dc7800 - Convertible Minitower PC Setup And Configuration Manual

Appendix B: Power / Sleep / Global States Explained

A computer can be in one of several power states under the Advanced Configuration and Power Interface
(ACPI) specification. These power states are also known as Sleep (Sx) states or Global (Gx) states.
•
S0 is the ON state. The computer is fully functioning. All system devices and operating system, if
available, are running. S0 is also known as G0.
•
S3 is the Standby (Microsoft terminology) or Suspend-to-RAM state. The memory subsystem and Vaux
power rail remains powered, while the rest of the system, including the processor, is not powered.
When the system resumes from S3, the system context remains intact because system memory was
preserved and powered at all times.
•
S4 is the Hibernate (Microsoft terminology) or Suspend-to-Disk state. The system context (memory) is
saved to the hard drive as a hibernation file. When the system resumes from S4, the system context is
restored from the hibernation file. Vaux remains powered, but all other subsystems including system
memory and the processor are not powered.
•
S5 is the Soft Off state. It is identical to S4 with the exception that the system context is not saved.
When the system resumes from S5, it powers up and going through POST. S5 is also known as G2.
•
G3 is the Mechanical Off state. All subsystems are not powered in this state. The easiest way to
achieve this state is by removing AC power from the system by unplugging the power cord.
The ME has its own power states (Mx) similar to the Sx states:
•
M0 is the ON state for the ME when the system is in S0 state. The ME is fully powered and running.
•
M1 is the ON state for the ME when the system is in a non-S0 state. The ME is fully powered and run-
ning.
•
Moff is the OFF state for the ME. The system is in a non-S0 state.
The ME can be set to stay powered and active in all Sx states. If the system (host) is in S0, then the ME
will be in the corresponding M0 state. However, if the system is in S3, S4, or S5, then the ME will remain
active, but it will be in M1 state.
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