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Squeezing More Life Out of Your Notebook's Battery Part II

Persuading Mobile CPUs To Conserve Energy

Windows allows users to adjust CPUs' use and power savings. The interface for such controls appears under the Power Schemes tab in the Power Options section in Control Panel.

Windows XP gives users various ways to control CPU behavior.

The following table presents an overview of how the individual settings work on CPU clock rates, and thus also exert an indirect influence on energy consumption and battery lifetime.

Windows XP Power Schemes
Operating mode: AC Power
Name of power schemeClock controlClock rate
Home/Office Desktopfixed(1860 MHz)
Portabel Laptopadaptive(800 <> 1860 MHz)
Presentationadaptive(800 <> 1860 MHz)
Always onfixed(1860 MHz)
Minimal Power Managementadaptive(800 <> 1860 MHz)
Maximum Batteryadaptive(800 <> 1860 MHz)
Operating mode: Battery
Name of power schemeClock controlClock rate
Home/Office Desktopadaptive(800 <> 1860 MHz)
Portable Laptopadaptive(800 <> 1860 MHz)
PresentationDegrade(800 MHz)
Always onfixed(1860 MHz)
Minimal Power Managementadaptive(800 <> 1860 MHz)
Maximum BatteryDegrade(800 MHz)

Overview of the effects of various power schemes when operating from AC power or the battery using the Pentium M750 as an example.

We assume that the user has the option to choose if the CPU runs with: