Build a Clean, 'Green' Machine

The Advanced Configuration and Power Interface, or ACPI, is an open industry specification co-developed by Hewlett-Packard, Intel, Microsoft, Phoenix, and Toshiba. ACPI defines several modes of operation that can reduce power consumption and increase operational efficiency for properly designed components. Each component can be placed in varying states of sleep—otherwise called "suspend" or, in some cases, "hibernate"—to make this possible.

In commercializing ACPI, Intel has gone with the trademarked term SpeedStep. AMD uses its own trademarked term, Cool'n'Quiet. Both refer to proprietary but well-intentioned designs to limit power-consumption when systems aren't heavily loaded.

Essentially, each stage of suspend eliminates power to some core component until even the CPU and memory no longer draw power. This flexibility allows for a broad range of power profiles to suit numerous conditions and purposes. It also means that—in exchange for being willing to wait a bit longer to wake back up and return to an active, capable state—users can trade lower power-consumption levels over time for more battery life on mobile devices or to lower their desktop gear electric bills.

The following tables shows ACPI suspend states for processors. Keep in mind that the analogy with ever-deeper levels of sleep is pretty apt: The lower the power consumption goes, the more time and energy it takes to "wake" a system back up to a normal, full-powered and operational state. Delays can range from short fractions of a second in light suspend states to as long as 30 seconds in deep suspend states—even longer when the device is completely turned off.

ACPI PROCESSOR SUSPEND STATES
C0	Fully-operational state (powered on)
C1	Halt; not executing instructions, can reach execution state instantly
C2	Stop-Clock; CPU maintains software-visible state, slower to awaken
C3	Sleep; no cache-coherency but maintains other operational states

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The next table describes ACPI suspend states for devices:

ACPI DEVICE SUSPEND STATES
D0	Fully-on operational state
D1	Intermediate power state (individually defined)
D2	Intermediate power state (individually defined)
D3	Fully-off non-operational state (unresponsive to its corresponding bus)

By setting specific thresholds of system activity based on CPU load, disk activity, display use, and so forth, these schemes basically instruct systems (or components) when to increase or decrease their power consumption levels. They also instruct systems when to start descending the ladder of suspend states, as described in the two preceding tables, as inactive systems become increasingly inert and unresponsive to user input and activity. These schemes are designed to minimize power consumption. On portable PCs, this has the nice side effect of also extending battery life. On desktop PCs, this offers equally attractive energy savings overall, which is particularly appealing for machines that must be left powered-up at all times.

More Green Tips

Another green option: You can purchase green PCs, such as Computer Technology Link's CTL Meridian SL700, which was released in late 2005. The SL700 reportedly consumes as much as 20 percent less energy than most PCs, operates at low-decibel sound levels, features a lead-free Intel 945GTPL motherboard, and ships with an end-of-life coupon for free recycling services (once the unit falls into disrepair).

Build green PCs by using green parts wherever possible and by choosing best-of-breed components as measured by their electrical efficiency, power-management facilities and environmental friendliness. This must be accompanied by provisions for proper disposal of equipment that has out-served its usefulness. You can instruct clients and users on how to properly dispose of old systems. Even better, include provisions for proper disposal as part of the sale. For more on this topic, see this recent TechBuilder related Recipe Recycle Old Hardware the 'Green' Way.

By deploying energy-efficient and environmentally-friendly components, system builders can do a lot to green-up their builds and upgrades. By switching from energy-hungry CRT displays to more energy-efficient LCD displays, you can green-up things even more. Make sure to take advantage of power-management modes, particularly sleep states and hibernation modes, to lower power consumption to the absolute minimum while PCs are idle. Low-consumption states are not just for laptops anymore!

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SIDEBAR: Additional Green Resources

System builders can turn to some great Web sites for more information, product ratings, and reviews on sites that specialize in quiet or green PCs. Here are some recommended resources:

• Green Office Guide: This U.K. site offers an excellent animated resource on the safe disposal and maintenance of common computing environments.

• SilentPCReview.com: Founded by Mike Chin, this site is dedicated to reviews, news and information about quiet, low noise, and/or silent computers and components, as well as their energy efficiency and thermal performance.

• Energy Star-compliant computers: Search through the official listings online via pull-down menus, which offer choices of product type, brand and OS.

• The European Union's Eco-Label for PCs: The Eco-Label program is more stringent than it's U.S.-based counterpart Energy Star. Consequently, the PCs and components listed will be more expensive, but they will be a bit greener.

• The Electronic Industries Association (EIA): This non-profit consortium lists agencies and corporations that recycle used computing equipment on its consumer education initiative page, and also provides information about potentially toxic materials.

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ED TITTEL is a freelance writer and trainer in Austin, Tex., who specializes in Windows topics and tools, especially networking and security related matters. JUSTIN KORELC is a long-time Linux hacker and Windows maven who concentrates on hardware and software security topics. Ed and Justin are also co-authors of Build the Ultimate Home Theater PC (John Wiley, 2005).