Hardware Reference
In-Depth Information
Asmentioned,manypeoplehavebeenusingthiscapabilityonlaptops,butfewseemtobe
aware that you can use it on desktop systems also. To enable this deeper sleep capability,
there are only two main steps:
1.
Enter the BIOS Setup, select the Power menu, locate the ACPI suspend setting, and
set it to enter the S3 state (sometimes called STR for Suspend to RAM). Save, exit,
and restart.
2.
In Windows, open the Power Options tool in the Control Panel, locate the setting for
the Power button and change it to Sleep or Stand by.
Youcan also take advantage ofhibernation, which allows youto use the ACPI S4 (STD =
Suspend to Disk) state in addition to S3. ACPI S4 is a lot like S3, except the system con-
text is saved to disk (in a file called hiberfil.sys) instead of RAM, after which the system
enters the G2/S5 state. The G2/S5 state is also known as Soft-Off, which is exactly the
same as if the system were powered off normally. When you power on from Hibernation
(S4),thesystemstillcoldboots;however,ratherthanreloadingfromscratch,Windowsre-
stores the system context from disk (hiberfil.sys) instead of rebooting normally. Although
hibernating isn't nearly as fast as S3 (Suspend to RAM), it is still much faster than a full
shutdown and restart and works even if the system loses power completely while suspen-
ded. Windows XP and earlier allows you to place a system in Standby (Sleep) or Hibern-
ate modes, while Windows Vista and later has Sleep, Hibernate, and Hybrid Sleep modes.
HybridSleepisacombinationofsleepandhibernate,wherethesystemstateissavedboth
in RAM and to the hard disk as a backup. Hybrid Sleep is the default Sleep function set-
ting for desktop systems, and because of the extra time to create the hiberfil.sys file it un-
fortunately makes the system take just as long to Sleep as it does to Hibernate. To speed
up the Sleep mode functionality in Windows 7/Vista you can disable Hybrid Sleep.
Finally, to make the system Sleep automatically, you can change the Windows Power
SchemesettingstoputthesysteminSleepmodeafteratimedurationofyourchoice.This
allowsthesystemtoautomatically enterSleepmodeafterthepresetperiodofinactivity (I
usually set it for 30 minutes to an hour) has elapsed.
By using S3 Sleep mode, you can effectively leave the system running all the time yet
still achieve nearly the same savings as if you turned it off completely. Servers, of course,
should be left on continuously; however, if you set the system to Wake on LAN (WOL)
in both the BIOS Setup and in Windows, the system can automatically wake up anytime
it is being accessed. The bottom line is that taking advantage of Sleep mode can save a
significant amount of energy (and money) over time.
