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The Z77 EX 4's BIOS does not have a S1 Sleep setting, or really any specifically labeled Sleep state. The best you can do is set "Suspend to RAM" in the ACPI menu, to Auto, which will give you S3 Sleep. That is what wardog is using, and what I use.
S1 Sleep is not very useful, IMO. In S1, the CPU is still powered up, so the CPU cooler fan, and cooler pump if using water cooling, is still running. All the fans in the PC will be running too, so the PC is still on, but just not doing anything, as the CPU does not execute any instructions. I assume there are reasons for using S1, but for the standard PC user, I don't see the point.
S2 Sleep removes power from the CPU, but AFAIK the system fans and mother board is still powered up.
S3 Sleep stores the current state of the PC/OS in RAM, which is read when the PC wakes, and you start up where you left off when entering S3 Sleep. The CPU is powered down completely, so needs no cooling. All fans in the PC are shut off, as well as drives, etc. Power is only applied to RAM memory, to maintain the image of the PC's state that was saved to RAM. If the PC loses power for some reason, then the image stored in RAM is lost, and the PC must be booted again.
S4 Sleep, or Hibernate, is the same as S3, but also writes the PC's state image to disk. This is used in laptops, but can be used on desktop PCs. The only difference is if power to the PC is lost, the image written to disk is used to restore the PC to its previous state.
The BIOS of most desktop PCs usually only have the S3 option. Windows has S4/Hibernate enabled by default, but you must select Hibernate when you choose to enter Sleep. S3 or S4 are really the only Sleep states that make sense for a PC user.
Från http://forums.tweaktown.com/asrock/52260-setting-sleep-mode-s...