This chapter is intended to help computer support personnel implement energy saving strategies in their offices. This includes both enabling power management and turning off computers at night and on weekends. Section 4.1 presents strategies that work for all computers, regardless of power management capability. Section 4.2 focuses on identifying computers with power management capability and enabling power management. Section 4.3 provides an overview of what we recommend for power management settings. Details of how to enable specific systems is presented in Appendix D, which covers x86, Apple, and Suns systems, as well as installing aftermarket devices. Figures 4.1 and 4.2 present decision-making flow charts of the most important questions to ask as you address power management on your PCs and monitors. Finally, Section 4.4 provides troubleshooting insights and suggestions for use when problems occur.

If you are not a computer support person at your company, you should consult them before changing some power management settings. They may have knowledge about your computing environment (and power management in particular) that can alert you to potential pitfalls, or to strategies that make power management work best in your environment.

4.1 Turn off computers at night and on weekends

One of the simplest and most effective ways to save energy is to turn off computers (PCs and monitors) when not needed, especially nights and on weekends. Sometimes computers are left on for legitimate reasons-for automatic backup or remote access, for example. However, many computers that could be shut off are left on by users who either mistakenly believe that shutting off their computer is harmful to the equipment or who simply forget to turn them off.

The belief that frequent shutdowns are harmful persists from the days when hard disks did not automatically park their heads when shut off; frequent on-off cycling could damage such hard disks. Conventional wisdom, however, has not kept pace with the rapid technological change in the computer industry. Modern hard disks are not significantly affected by frequent shut-downs. Shutting down computers at night and on weekends saves significant energy without affecting the performance, and may increase (rather than decrease) the operating lifetime of the equipment.

In cases where the computer is deliberately left on for network services or remote access, the monitor can be safely shut off without interfering with those activities. Since the monitor can consume two or three times as much electricity as the PC, turning off monitors is a big step in achieving significant energy savings.

Misinformation and bad energy habits are major stumbling blocks to achieving these energy savings. Computer users need to be informed about the real effects of shutting down their computers. Appendix B provides some resources for educating computer users about the benefits of shutting off their equipment at night and on weekends.

4.2 Determining Power Management Capability and Enabling Power Management

Specific instructions for checking and enabling power management are presented for many common systems in Appendix D. They explain how to check if your current PCs and monitors are capable of power management, if they are enabled, and how to best configure them for your needs.

Before changing the power management configuration on a machine, you may want to record the current power management settings. This will reassure the user that the previous machine mode can always be reconstructed if any changes that are made create problems.

Table 4.1 shows the methods for changing power management configuration that are applicable to each system (hardware and software) type. Find the row which matches the hardware and software for your system to see which sections of Appendix D have applicable instructions. As the table shows, in most cases there are several mechanisms that can be used to enable power management. In most cases, it is only necessary to enable power management through one of them. For example, either the BIOS timer or a screensaver program (accessed through a control panel) can initiate monitor power management on an ENERGY STAR PC. In most cases, it is easier to configure power management through the operating system rather than through BIOS; however, this is not always possible. If power management is enabled through more than one mechanism, the power management signals may be inconsistent or interfere with one another. In some cases it may be necessary to enable power management with several methods, in several places, in order for it to work.

To properly check and enable power management, you will want to know the operating system, the BIOS type (for x86 machines), the screensaver software, and any other software used for power management. The operating system used should be immediately apparent. You do not need to know the BIOS type by name, but can match your BIOS to one of several typical systems we describe in Appendix D. Identifying the screensaver, video card control program or other software for monitor power management is discussed in Appendix D.

4.3 Overview

In general, we recommend the delay times for power management shown in Table 4.2, though you may discover that shorter or longer times better suit your own needs (all times consecutive). IRQ settings for keyboard and mouse activity (see Section D.2) should be enabled, so that they can trigger activity and reawaken the system. Unless specific problems arise with particular IRQs, it is best not to tamper with manufacturer default settings.

4.4 Trouble Shooting

In the past, the only solution to many power management related problems was to disable power management entirely. This is no longer the case. Power management is now more flexible and has more options, which allows specific problems to be addressed without disabling all power management features.

When making trouble shooting decisions, it is important to weigh the potential energy savings against the costs of a particular power management option (in terms of recovery time and system interference). Both savings and costs depend on how the computer is used, but a few general guidelines should be kept in mind. Power management of monitors typically saves more energy than it does for PCs (unless the monitor is turned off nights and weekends but the PC is left on). Monitor power management is less likely to be defeated by network activity, and is also less likely to cause problems than PC power management. Even if there is some reason why the PC can't accomplish power management, or power management interferes with use of the PC and has to be disabled, the monitor can usually still be power-managed. People who are particularly fond of their screen art should try to configure the system to display the screensaver for a few minutes, then begin the power management cycle (some screensavers can do this; in other cases the screensaver and BIOS can work together).

Many PC power management functions have no discernible delay in returning to full power, so that it can be difficult to determine if power management is working. To be certain that power management is occurring, it is necessary to actually measure the power the system uses (see Appendix D), which is not a realistic option in most offices. Apart from that, the most obvious feedback of a PC powering down is hearing the hard disk power down and spin back up. Recovery from 'doze' modes is nearly instantaneous, and even lower-power modes have very quick recovery times, making it difficult to be sure that PC power management is occurring.

If the recovery from a blank screen is instantaneous, then the monitor is probably not in a suspend mode (the lowest power state), though it could be in the first power management mode, sleep. Some monitors will "beep" as they revive, and others signal low-power modes with an indicator light on the front of the monitor. Check the manual to see if any such indication happens automatically (or is optional) during low-power modes.

There are many reasons this could be occurring, including:

• The 'main switch' for power management is on, but subsidiary switches (e.g., for each low-power mode) are off. Turn these on and see if power management occurs (see Figure 4.1; the switches are generally found in BIOS setup screens).
• The timers are set to such long delays that the power management does work but rarely has the opportunity. Try reducing the delay times.
• The network (or network operating system) is keeping the PC awake. To diagnose the problem, try rebooting the machine with the network cable disconnected, or even with the network card removed to see if this changes power management behavior; also check the network operating system documentation. A different network card may not have this problem, but the replacement cost may be greater than power management savings warrant.
• The operating system may not support power management.
• The PC may have been upgraded in a way that interferes with power management. If it was custom built, rather than a standard model from a manufacturer, parts may not properly work together to accomplish power management. There may be no solution to this problem.
• If the monitor is not entering sleep mode, it may not be capable of power management, or a screensaver may be interfering with power management operation. To help diagnose the problem, try temporarily using a monitor that you know works well with power management, and changing screensavers to the blank screen option.
• Application software is keeping the system awake. For example, some software for controlling CD-ROM drives will poll the drive frequently to see if a disk has been inserted; some printer software routinely polls the printer for its status. Disabling an IRQ may alleviate this, but the system may go to sleep while a CD is playing, or while a long print job is in progress.

The machine may be configured to operate this way for a good reason, such as to avoid network problems or avoid long recovery delays. However, it is also possible that there is no good reason for the settings. Try to determine why the machine was configured how it was, and whether it can be set to more typical settings, such as those recommended in this guide.

In certain environments power management can cause problems, and it may be necessary to leave power management disabled. However it is important to address specific complaints (e.g., "The hard disk spins down every five minutes and takes forever to spin back up") rather than general ones ("Power management is causing problems"). It may be possible to fix specific problems by changing power management settings. General problems may not be the fault of power management at all. Power management is often a convenient scapegoat for system problems, sometimes resulting in power management being unnecessarily disabled.

It is important to keep in mind that users who have had trouble with power management in the past (or have heard stories from others who have had problems) are often distrustful of the technology, even though great improvements have been made. Educating users about power management will make them more comfortable with the technology.

This can be caused by some screensavers. If that is the case, the screensaver can usually be reconfigured to not do this. Avoid screensavers or screensaver options that require hard disk access, and make sure that the screensaver delay time is less than the first monitor power management delay time. Some networks can cause a machine to reawaken after a short period of power management. See if the machine power manages correctly when not connected to the network, and if so, if the server or network card can be reconfigured.

This occurs if the PC goes into the doze mode, slowing the processor clock, while the computation is in process. If such calculations are rare, then either doze or power management in general can be disabled while it is in process. If the computer is routinely used in this way, disable doze only so that the rest of power management will occur.

That machine might not be capable of power management. PCs that appear similar on the outside can be quite different on the inside, so that even if one PC in the office has power management, a similar PC might not. Try calling the manufacturer and provide them with the serial number to help determine if the machine has power management features.

Consider changing the power management settings with the user present so that she can be reassured that the changes are acceptable.

Check the BIOS settings. The interrupt requests for the keyboard or mouse may not be enabled (these are typically IRQ1 and IRQ12 respectively).

Power management may be slowing CPU activity too much for it to respond to network activity. Some versions of BIOS have options to specify how much to reduce the processor speed in doze or standby. Try reducing the speed reduction value; this speeds up the processor (when in the low-power mode) and increases its ability to respond to network activity. If the problems persist, or if changing the speed is not an option, try disabling the doze or standby option.

If password protection cannot be disabled for security reasons, try increasing the delay time for hard disk spin down (to 15 minutes or more) in order to reduce the occurrence of the problem. If this is still unacceptable to the user, it may be necessary to disable the hard disk spin-down. The energy savings potential for the monitor are greater than from the hard disk, so keeping power management enabled for the monitor should be the priority.

DOS can override the BIOS. Try routinely turning the machine off or remaining in Windows.

One response to this situation is to move the back-up time to during the work day. Another is simply turn off the computer when not many files have been changed that day. A third response (on machines capable of it) is to have the system completely power down at a time at which the backup will have finished.

Consider increasing the delay times for the power management modes that are causing the problem. The hard disk recovery time is often a source of user complaints about excessive recovery time. If an auto-save feature is spinning up the hard disk while the person is typing, consider turning off that feature. Try increasing the delay time for the hard disk while keeping them as-is for the processor and monitor. Even if some power management methods must be disabled for the user, don't turn off all features-keep active the power management features that are not interfering with work.

A few models of PCs (most notably early Apple PowerMacs) shut off entirely rather than go to sleep. Few users find this acceptable, so be cautious about enabling this form of power management.

Continue to Chapter 5: How do I buy new ENERGY STAR computers?

Return to the PC User Guide table of contents and home page.

Return to Chapter 3: How Does Power Management Work?