Product Description 
 37 
Table 6 lists the system states based on how long the power switch is pressed, depending on how 
ACPI is configured with an ACPI-aware operating system. 
Table 6.  Effects of Pressing the Power Switch 
 
If the system is in this state… 
…and the power switch is 
pressed for 
 
…the system enters this state  
Off 
(ACPI G2/G5 – Soft off) 
Less than four seconds  Power-on 
(ACPI G0 – working state) 
On 
(ACPI G0 – working state) 
Less than four seconds  Soft-off/Standby 
(ACPI G1 – sleeping state) 
On 
(ACPI G0 – working state) 
More than four seconds  Fail safe power-off 
(ACPI G2/G5 – Soft off) 
Sleep 
(ACPI G1 – sleeping state) 
Less than four seconds  Wake-up 
(ACPI G0 – working state) 
Sleep  
(ACPI G1 – sleeping state) 
More than four seconds  Power-off 
(ACPI G2/G5 – Soft off) 
1.14.1.1 System States and Power States 
Under ACPI, the operating system directs all system and device power state transitions.  The 
operating system puts devices in and out of low-power states based on user preferences and 
knowledge of how devices are being used by applications.  Devices that are not being used can be 
turned off.  The operating system uses information from applications and user settings to put the 
system as a whole into a low-power state.