For PCs and monitors to successfully power manage, the hardware and software must support the technology (primarily by being ENERGY STAR compliant). Having compliant systems is the result of a responsive purchasing system. This chapter provides guidelines for purchasing power-managed computers and monitors.

When procuring new computer equipment, simple steps can be taken to ensure that it has power management features and that they work properly in your computing environment. The first step is to check if the models under consideration are on the EPA ENERGY STAR lists (see Appendix B for the web address and phone numbers). This usually will tell you if the models are ENERGY STAR compliant, though some compliant models may not be on the list (possibly because they are relatively new), and a few PC models have power management capable and non-capable variants under the same model name. Thus, you will want to confirm the results with the manufacturer.

Be sure to specify ENERGY STAR compliance on the purchase order. If you will be purchasing many PCs of a similar type, consider borrowing or purchasing one and testing it in your computing environment, with typical applications, network connections, etc., to insure that it power manages properly. Since the performance of power management varies depending on the configuration and the computing environment, field testing is really the only way to guarantee performance. Some PCs are put together by private assemblers; they may require extra attention to insure that power managing equipment is procured.

You should ask for documentation of the following:

• ENERGY STAR compliance. Make sure that the devices comply with the EPA ENERGY STAR program and not just a vague promise of (or label attesting to) "greenness".
• Description of power management features. This should include the role of power management, power modes, and energy consumption data.
• Instructions for operation of power management. This should include user instructions on how to configure power management through the operating system and the BIOS (Basic Input/Output System), as well as what settings are appropriate for typical offices.
• Known equipment interactions. The manufacturer should provide a list of any known problems or most asked questions and their answers.
• Low default time settings. The delay times set in the PC and monitor (as shipped) should be low, but not unreasonably so (for example, ten minutes between mode changes; see Section 4.3 for recommended times).
• Low low-power use: Look for PCs and monitors with low-power energy use levels that significantly exceed the 30 W ENERGY STAR standard. Many monitors, in particular, can power down to 5 W or less.
• Availability of on-line help. The availability of documentation resources on-line is becoming an increasingly important and useful way to find up-to-date and detailed information about your equipment.
• Feedback. Look for front panel lights that indicate when power management is occurring.

ENERGY STAR monitors must power down to 30 watts or less in sleep mode, however many new monitors can go much lower, such as to 5 watts or less in suspend mode. The ENERGY STAR list reports the sleep mode power consumption. An additional feature helpful to power management is the presence of on-screen controls. Power management time ranges should be adjustable. Inquire about how easy it is to adjust settings and what the defaults are. Check to see if monitors are DPMS or universal in signaling of power management. Universal monitors are preferred since they respond to both DPMS signals and blanked screen (from a screensaver, for example).

Other considerations in purchasing monitors include the location of the power switch. Research has shown that monitors are more likely to be switched off at night and on weekend when the power switch is located at the front of the device. Some monitors also provide an indicator light showing when the monitor is on but in low power mode. This feedback can improve the success of power management. Some monitors also have a suspend switch on the front, to enable the user to more easily put the machine in suspend mode manually.

The Swedish NUTEK specification for monitor power-down has more rigorous energy criteria than does the ENERGY STAR program, and also includes standards for radiation and other health and environmental factors. The standby level is 15 W, with a 3 second maximum recovery time, though standby is not required if the monitor uses less than 30 W when active. A lower power mode of 8 W is required after at most 70 minutes of inactivity. There is currently no separate NUTEK standard for the PC itself.

As shipped from the manufacturer, ENERGY STAR PCs must be capable of powering down below 30 W while idle, as shown on the ENERGY STAR list (though systems with an integral PC and monitor must power down to 60 W or below). However, as extra memory, disk space, or other peripherals are added, the power consumption will increase, so a compliant machine with many extras may use more than 30 W. When buying an add-on device for many systems, ask the manufacturer how much the item will increase your systems' energy use when full-on or when in suspend.

Monitors cannot power down by themselves and must rely on an external signal (from the CPU or a video card) to activate the low power modes. Generally, both the computer signaling output and monitor must be DPMS compatible for power management to occur. Verify that the monitor was tested with BIOS and operating system in the PC. The power management capability must be compatible with all CPUs supported by the monitor.

The ability to perform with computer networks is a critical part of successful power management. You should consider the following issues to address PC/network interaction.

• Network tested. Be sure to purchase PCs that have been tested with your network software. The ENERGY STAR list provides information on network testing, specifically for the Novell, Banyan Vines, Windows NT, and Lan Manager network systems.
• Network response. Power management should not lose network connections in low-power modes.
• Network software. It may be desirable for network management software to be able to send power management signals to (or check BIOS configuration on) individual PCs on the network.

Though desktop workstations are generally higher powered than a PC, they are still usually used primarily by one person, and so are good candidates for power management. Terminals, such as X-terminals, usually have fewer components than a PC, and so use less power, but their monitors will use the same power as a PC monitor of the same size, so that they are also still a good application for power management. Several companies offer machines in each category that can successfully power manage. See the ENERGY STAR list for specific products.

Servers generally consume more power than PCs. Because of this they rarely meet the ENERGY STAR criterion of 30 W in low power mode. Some of these machines may have power management, and so offer energy savings. However, because they are likely to be accessed at any time, they are less promising candidates than other types of computers for power management. Ask the manufacturer about power management in these devices.

Continue to Chapter 6: Future Directions.

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