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All about System Power States (S0-S5)

By Ajay Mungara (Intel) (111 posts) on January 10, 2007 at 3:03 am

The System Power States are often referred in the AMT documentation. This blog post attempts to explain the various System Power States (S0-S5).

The overall power consumption of the system is referred to as System Power States. There are a total of six different power states ranging from S0 (the system is completely powered ON and fully operational) to S5 (the system is completely powered OFF) and the States (S1, S2, S3 and S4) are referred to as sleeping states, in which the system appears OFF because of low power consumption and retains enough of the hardware context to return to the working state without a system reboot.

The key characteristics of the each state that we care about are:

• The overall Power the system consumes in a given state - Power Consumption.
• Retention of the system context (such as the volatile registers, memory caches, and RAM) - Context

Note on power state transition: System is Waking Up when the system is transitioning from the OFF State (S5) or any sleep state (S1-S4) to the ON State (S0) and the System is going to Sleep when the system is transitioning from ON state (S0) to OFF state (S5) or sleep state (S1-S4). Please note that the system cannot enter one sleep state directly from another, as it must enter the ON state before entering any other sleep state.

• System Power State S0 the ON state: The system is completely operation, fully powered and completely retains the context.
• System Power State S1 the Sleep state: The system consumes less power than S0 state. All Hardware & Processor context is maintained.
• System Power State S2 the Sleep state: The system consumes less power than S1 state. Processor loses power and processor context and contents of the cache are lost.
• System Power State S3 the Sleep state: The system consumes less power than S2 state. Processor & Hardware context, cache contents, and chipset context are lost. The system memory is retained.
• System Power State S4 the Hibernate state: The system consumes the least power compared to all other sleep states. The system is almost at an OFF state, expect for a trickle power. The context data is written to hard drive (disk)and there is no context retained.
• System Power State S5 the OFF state:The system is in a shutdown state and the system retains no context. Note that in power state S4 the system can restart from the context data stored on the disk, but in S5 the system requires a reboot.

Refer to the following documents for further information on System Power states

Architecture Guide, Network Interface Guide, MSDN Site

Categories: Manageability

Comments (6)

January 10, 2007 12:38 AM PST Nishant Mistry

The following line seems to have bug in it. See my comment below in [nishant: ] brackets: Note on power state transition: System is Waking Up when the system is transitioning from the OFF State (S0) [nishant: needs to be S5] or any sleep state (S1-S4) to the ON State (S5) [nishant: needs to be S0] and the System is going to Sleep when the system is transitioning from ON state (S0) to OFF state (S5) or sleep state (S1-S4). Please note that the system cannot enter one sleep state directly from another, as it must enter the ON state before entering any other sleep state.

January 10, 2007 3:51 AM PST Ajay Mungara (Intel) Total Points: 8,142 Status Points: 8,142 Community Manager

Hi Nishant, Thanks for pointing out the mistake/typo. I will fix the sentence and repost the blog. Thanks again.

February 2, 2007 12:04 PM PST Juan Torres

Hello Ajay, I would ask you for a problem I have. It is related to your article. My system, based on 965 intel chipset (revision C1), lockup when starts from time to time. That's to say, when it starts from S5 state. The system not enter in bios..., nothing, althoug computer fans and leds are running, but no boot. When computer boots and no fail, the OS works fine. In the following article I see that there is a problem with 965 chipset related to the boot/shutdown procedure: ftp://download.intel.com/design/chipsets/specupdt/31305403.pdf I'm sorry if it is not the correct place to put my question, but I would like you confirm me the if problem I have could be related to the 965 error. Thank you very much in advance.

February 2, 2007 3:44 PM PST Ajay Mungara (Intel) Total Points: 8,142 Status Points: 8,142 Community Manager

Hi Juan, I have posted your question in our developer discussion forum. http://software.intel.com/en-us/forums/manageability-softwar.....pic/53085/ Please monitor the same for a response from our technical experts. Regards, Ajay Mungara

December 10, 2007 6:56 AM PST Joachim

Maybe a late addition, but S4 shouldn't draw more power than S5. Even in S5, your system will consume some trickle power, but in both states (S4 and S5), you can unplug the compter as long as you like, and still have the same behaviour after plugging it back in (Bootup from S5 and resume from hibernation in S4).

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