| Tell me everything I need to know about hibernate (s4) and standby (s3) modes: |
Both hibernate and standby modes put the PC into a low power usage state that can be resumed from quickly, returning the computer to the state that it was in when the standby event occured.
Media Center uses these modes to allow the machine to automatically wake to record a scheduled program. Once the recording is complete the machine then returns to the users nominated sleep mode, thereby saving power when not in use.
s4 mode (hibernation) has the following properties:
- stores the contents of ram to the Hard Disk Drive prior to powering off.
- The entire system is powered down in this state.
- System performs a full Power On Self Test
on resume from Hibernation.
- Has advantages in that a power failure will not destroy the Hibernated state of the machine (data stored on disk).
- Can take some time to resume dependant on the size of ram and the speed of the disk that the memory image is read from.
- Typically works better on some systems due to the complete Power On initialisation on startup.
- Uses no power in it's sleep state.
s3 (standby) mode has the following properties:
- Memory contents are kept active on chip.
- The system is powered down except for minimal power to keep the ram active.
- System does not perform a Power On Self Test
on resume.
- A Power Failure will destroy the standby state of the machine.
- Resumes very quickly as no POST is performed and no data must be read from disk to re-populate memory.
- Is prone to be more problematic to get working properly.
- Uses minimal power to keep the system memory active.
Both modes provide the following functionality:
- +5vsb settings. This setting is usually achieved by jumpers on the motherboard. When active +5 volts of power is supplied to USB devices. This allows the PC to detect power on events from USB remote controls and/or keyboards/mice. Consult your motherboard manual for advice on how to set these jumpers for specific USB ports.
- PC can be woken from either state (s3) or (s4).
- PC will wake automatically from either state to perform scheduled activity.
How does the PC know when to wake up?
- Any task on the PC that is required to perform an action at a given time will report that action to windows at the time the system goes into hibernation or standby. The system then programs the standby timer on the motherboard to countdown until such time as the first scheduled task is due to take place. When the timer reaches 0 the machine will automatically wake. Waiting tasks will then check the current time and perform any actions as normal.
The standby timer is a bios level function powered by the bios battery and is therefore protected from power failures.
Last updated: 03 Dec, 2008
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