System Sleep States: S0, S1, S2, S3, S4 & S5

[The_Big_K]

CEans,

CS engineers over here might be able to throw some light on system sleep states S1 - S5 and why these states are needed.

I'm quite sure lot of us do not know about these sleep states!

[yudi]

The states are represented as follows

S1 - Stand By (Power On Suspend) - no system context is lost

S2 - Stand By - CPU and system cache context is lost


S3 - Stand By (Suspend to Ram) - system memory context is maintained, all other system context is lost


S4 - Hibernate - Platform context is maintained.

States S1, S2, and S3 are all various aspects of the Sleep function. If you are running an incompatible video card, some or all of these states will be unavailable.

[gauravtiwari89]

S1: the most power-hungry of sleep-modes. All processor caches are flushed, and the CPU(s) stop executing instructions. Power to the CPU and RAM is maintained, Basically old machines are more likely to support S1.

S2: The CPU is powered off, this state is rather less found.

S3:In this state, RAM is still powered, although it is almost the only component that is. Since the state of the operating system and all applications, open documents, etc. lies all in main memory, the users can resume work exactly where they left. The computer is faster to resume than to reboot, secondly if any running applications have information this will not be written to the disk, This state is comparatively more common.

S4: In this state, all content of main memory is saved to non-volatile memory such as a hard drive, preserving the state of the operating system, all applications, open documents etc. That means that after coming back from S4, the user can resume work where it was left off in much the same way as with S3. The difference between S4 and S3, apart from the added time of moving the main memory content to disk and back, is that a power loss of a computer in S3 makes it lose all data in main memory.

S5: Soft Off-- Some components remain powered so the computer can "wake" from input from the keyboard, LAN, or USB device.


Cheers.....