Power Supplies - Upgrading and Repairing PCs - page 915

Devices carrying the ENERGY STAR logo generally use 20%-30% less energy than required by
federal standards. In addition to ENERGY STAR, many European-targeted products are labeled with
TCO Certification, a combined energy usage and ergonomics rating from the Swedish Confederation
of Professional Employees (TCO).
Starting in 2007, the ENERGY STAR Computer 4.0 specification required the use of a power supply
that meets the 80 PLUS standard. In 2009, the 5.0 specification was released and now requires a
power supply meeting the 80 Plus Bronze standard, for a minimum of 85% efficiency (at a 50% load).
The 6.0 specification was published in 2013, along with new computer categories with different
allowable power ratings to match the type of systems currently on the market.
Advanced Power Management
Advanced Power Management (APM) is a specification jointly developed by Intel and Microsoft that
defines a series of interfaces between power management-capable hardware and a computer's OS.
The final version 1.2 of APM was released in 1996. When it is fully activated, APM can
automatically switch a computer between five states, depending on the system's current activity. Each
state represents a further reduction in power use, accomplished by placing unused components into a
low-power mode. The five system states are as follows:
• Full On —The system is completely operational, with no power management occurring.
• APM Enabled —The system is operational, with some devices being power managed. Unused
devices can be powered down and the CPU clock slowed or stopped.
• APM Standby —The system is not operational, with most devices in a low-power state. The
CPU clock can be slowed or stopped, but operational parameters are retained in memory. When
triggered by a specific user or system activity, the system can return to the APM Enabled state
almost instantaneously.
• APM Suspend —The system is not operational, with most devices unpowered. The CPU clock
is stopped, and operational parameters are saved to disk for later restoration. When triggered
by a wakeup event, the system returns to the APM Enabled state relatively slowly.
• Off —The system is not operational. The power supply is off.
APM requires support from both hardware and software to function. In this chapter, you've already
seen how ATX-style power supplies can be controlled by software commands using the Power_On
signal and the 6-pin optional power connector. Manufacturers are also integrating the same type of
control features into other system components, such as motherboards, monitors, and disk drives.
OSs that support APM trigger power management events by monitoring the activities performed by
the computer user and the applications running on the system. However, the OS does not directly
address the power management capabilities of the hardware. All versions of Windows from 3.1 up
through XP include APM support; however, support for APM was dropped from Vista and later,
which exclusively support the Advanced Configuration and Power Interface (ACPI) instead.
Advanced Configuration and Power Interface
As power-management techniques continued to develop, maintaining the complex information states
necessary to implement more advanced functions became increasingly difficult for the BIOS.
Therefore, another standard was developed by Intel, Microsoft, and Toshiba. Called Advanced
Configuration and Power Interface (ACPI) , this standard was designed to implement power-