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Understanding Remote Wake-up
The ability to remotely wake computers is an important development in computer management. This feature has evolved over the last few years from a simple remote power-on capability to a complex system interacting with a variety of device and OS power states.
In early implementations, the system could be started from a power off state by sending a "Magic Packet*." The Magic Packet contained the adapters MAC address repeated 16 times in the data field. The adapter, which was supplied with power from a standby power supply when the computer was turned off, would react to a "Magic Packet" containing its own MAC address by toggling a signal connected to the computer power control circuitry. The power control circuitry, in response, would activate power to the computer resulting in the computer booting the OS. This allowed network administrators to perform off-hours maintenance at remote locations without sending a technician out.
This early implementation did not require an OS that was "aware" of remote wake-up. However, it did require a computer that was equipped with a standby power supply and had the necessary circuitry to allow the remote power control. These computers were typically equipped with a feature named APM (Advanced Power Management). APM provided BIOS-based power control.
Newer computers feature ACPI (Advanced Configuration and Power Interface), which extends the APM concept to allow the OS to selectively control power by individual components. ACPI supports a variety of power states. Each state represents a different level of power, from fully powered up to completely powered down, with partial levels of power in each intermediate state. Here is a quick synopsis:
| S0 |
On and fully operational. |
| S1 |
System is in low power mode (a.k.a. sleep mode). The CPU clock is stopped, but RAM is powered on and being refreshed. |
| S2 |
Similar to S1, but power is removed from the CPU. |
| S3 |
Suspend to RAM (a.k.a. standby mode). Basically, most components are shutdown except RAM. |
| S4 |
Suspend to disk (a.k.a. hibernate mode). The memory contents are swapped to the disk drive, and then reloaded into RAM when the system is awakened. |
| S5 |
Power off. |
Some newer ACPI aware operating systems, such as Microsoft* Windows* 98, Windows* Me, Windows* 2000, Windows* XP, and Windows Vista*, support remote wake-up from standby or hibernate mode. Remote wake can be initiated by a variety of user selectable packet types and is not limited to the Magic Packet format. See operating system settings below.
Wake-up packets are typically sent by network management programs. However, you may be able to find simple programs available for download on the Internet at no charge that can be used for this purpose.
BIOS Settings
There are various settings in the computer BIOS that may need to be configured before remote wake-up will work.
Many ACPI computers can be configured to work in APM mode. Check your BIOS settings to determine your operating mode.
In both APM and ACPI computers, you may find settings for Wake on LAN (WOL), generally under the Power Control area and titled "Wake on LAN" and/or "Wake on PME." To enable remote wake-up, you should enable the setting that corresponds to the your adapter connection.
In ACPI computers, if you are using an ACPI aware OS (such as Windows* XP), and wish to be able to power up the system from a power off state, look for an ACPI specific setting such as "Wake on LAN from S5" and enable it.
Operating System Settings
Microsoft* Windows Products
Microsoft Windows NT* and Windows* 95 are not ACPI capable. Some settings will not be available in these operating systems. See also the "Other operating systems" section below.
Microsoft Windows 98, Windows Me, Windows 2000, Windows XP, Windows Vista are ACPI capable. These operating systems do not support wake from S5 state, only from standby. However, in some ACPI capable computers, the BIOS may have a setting that allows you to wake from an S5 state anyway. If there is no support for wake from S5 state in your BIOS settings, then you will be limited to wake from standby when utilizing these operating systems in ACPI computers.
In the adapters advanced settings, there is a setting titled "Enable PME." To explicitly allow wake up with a Magic Packet from shutdown under APM power management mode, set this to "Enable."
In ACPI capable versions of Windows, there will also be a setting titled "Wake on Settings." This controls the type of packets that will wake up the system from standby. Click the Help button in PROSet for a complete explanation.
In ACPI computers running ACPI aware operating systems such as Windows* XP, in Device Manager, the adapter properties will display a tab titled "Power Management." The setting "allow this device to bring the computer out of standby" should be checked.
Other Operating Systems
In operating systems that do not support remote wake-up technology, you can still utilize the "Magic Packet" method of remotely powering up a computer. When the computer is first powered on, the Intel® Boot Agent configuration utility can be invoked by entering CTRL-S when the Boot Agent prompt appears on the screen. The configuration program has a parameter setting titled "Legacy OS Wakeup Support." If this setting is enabled, the Boot Agent will pre-condition the adapter to respond to a "Magic Packet" wake up event. This allows remote wake-up in operating systems that do not support it.
NOTE: The "Legacy OS Wakeup Support" parameter was not available in early versions of the Intel Boot Agent. To update your Boot Agent to the latest version, download the archive PROBOOT.EXE from support.intel.com and follow the included instructions.
This applies to:
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