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Server Board Features 25
ACPI features include:
• Plug and Play (including bus and device enumeration)
• Power management control of individual devices, add-in boards (some add-in boards may
require an ACPI-aware driver), video displays, and hard disk drives
• Methods for achieving less than 15-watt system operation in the power-on/standby
sleeping state
• A soft-off feature that enables the operating system to power-off the computer
• Support for multiple wake-up events
• Support for a front panel power and sleep mode switch
The Server Board S875WP1-E supports sleep states S0, S1, S2, S3, S4, and S5. When the server
board is operating in ACPI mode, the operating system retains control of the system and the
operating system policy determines the entry methods and wake-up sources for each sleep state.
Sleep entry and wake-up event capabilities are provided by the hardware but are enabled by the
operating system. The following is a summary of the supported sleep states:
• S0: Normal running state.
• S1: Processor sleep state. No context will be lost in this state and the processor caches will
maintain coherency.
• S3: Suspend to RAM (Instantly Available PC Technology).
• S4: Hibernate or Save to Disk. The memory and machine state are saved to disk. Pressing the
power button or another wake-up event restores the system state from the disk and resumes
normal operation. This state assumes that no hardware changes were made to the system while
it was off.
• S5: Soft off. Only the RTC section of the chipset is running in this state.
CAUTION
The system is off only when the AC power is disconnected.
Table 8 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 8. Effects of Pressing the Power Switch under ACPI
If the system is in this state…
…and the power switch is
pressed for
…the system enters this state
Off
(ACPI S5 – Soft off)
Less than four seconds Power-on
(ACPI S0 – working state)
On
(ACPI S0 – working state)
Less than four seconds Soft-off/Standby
(ACPI S1 – sleeping state)
On
(ACPI S0 – working state)
More than four seconds Fail safe power-off
(ACPI S5 – Soft off)
Sleep
(ACPI S1 – sleeping state)
Less than four seconds Wake-up
(ACPI S0 – working state)
Sleep
(ACPI S1 – sleeping state)
More than four seconds Power-off
(ACPI S5 – Soft off)