The S3 advantage
Enabling S3 sleep state in the BIOS
Enabling Wake On LAN
- Open Device Manager.
- Find the NIC that you want to be able to perform Wake On LAN and open its properties sheet.
- Go to the Power Management tab of the Properties sheet.
- Check Allow This Device To Wake The Computer, as shown above. If you find that your computer will not stay in the sleep state, you may need to check Only Allow Management Stations To Wake This Computer.
Creating a power plan
- Open System and Maintenance in Control Panel and select Power Options.
- Click Create A Power Plan on the left sidebar, as shown above.
Selecting and naming your plan
- Select the power plan you want to start with. (In this example, I will use High Performance.)
- Name your plan and click Next.
Editing your plan
- Click Change Advanced Power Settings.
- To change Require A Password On Wakeup, click Change Settings That Are Currently Unavailable.
- Set the Turn Off Hard Disk After option to a value less than or equal to the time for the PC to sleep, for maximum power savings. Note: having the hard drives turn off while you are still using the computer can cause significant slowdown as they spin back up. It is recommended to set this equal to the time needed to go to sleep.
- Set Sleep After equal to the time you set on the basic power plan settings screen.
- Make sure that Allow Hybrid Sleep is set to On. This allows a combination of S3 (low power) and S4 (Hibernate) to be used. That way, if the computer loses power, no work is lost. This is, of course, at the expense of a small bit of hard drive space. In my opinion, there is no reason not to use this setting.
- Set Turn off Display After to the same value entered on the basic power plan settings screen.
- Click OK on the Advanced Power Settings screen.
- Click the Save Changes button on the Basic Power Plan Settings screen.
- To minimize the CPU's power draw under light load, edit the Minimum Processor State setting under Processor Power Management. To scale it back even under heavy load, change the setting for Maximum Power State.
Testing the new settings
To test the new settings, simply leave the computer alone for the specified amount of time. You will hear the computer get extremely quiet; this is because all of the fans and hard drives have been stopped. If you still hear fans or drives, go back and check your settings, particularly your BIOS settings.
Waking up the computer
Finding the MAC address via ipconfig /all
- Depicus: A Wake On LAN utility written in .NET. There is also a Web-based version, which you can use on the company's Web site or download and install on your own Web site. Additionally, non-.NET versions are available, including a Macintosh version. Note: the Web site and the software will send to the broadcast for the network.
- RemoteWakeup.com: A simple, Web-based Wake On LAN system.
- wakeonlan: The wakeonlan Perl script lets you wake computers as well with the Magic Packet and will run on any computer with Perl installed.
Enabling S3 sleep state in the BIOSSome BIOSes require S3 sleep state to be enabled or configured within the BIOS before the operating system can take advantage of it. Many modern motherboards do not require (or even contain settings for) this configuration. Your best bet is to check your BIOS' settings, looking in particular at the Power section. Key words to look for are "S3," "Sleep," "Wakeup," and "Resume." The image above shows an American Megatrends BIOS and its S3 settings section.
Justin James is the Lead Architect for Conigent.