Windows 95/98

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Advanced Configuration and Power Interface (ACPI)

Window 98 provides an updated Power Management functionality for both fully On-Now systems and for legacy Power Management as provided by Advance Power Management (APM) version 1.1 and 1.2. Using the Win32 Driver Model, power management for devices has been incorporated into every WDM driver. This allows Windows 98 to communicate with each device to determine its power state and if it is safe, put it into a low-power mode.

ACPI

ACPI was designed to address the shortcomings of previous power management plans. ACPI requires changes in both the BIOS and the chipset on the motherboard for full implementation. It should be noted, during the beta testing, only one such motherboard chipset, the Intel 430TX, was available to the public. There was not a publicly available BIOS that supported ACPI. There maybe instances where the customer will need to upgrade their BIOS for full ACPI functionality.

ACPI names four power management states, D0-D3. The states are related to each other in terms of power used versus context retained. Context is defined as information on the condition of the device. For example, a device that loses its entire context will need to be reinitialized to resume functionality. Each state is defined in the ACPI specification as shown below.

D3

Off: Power has been fully removed from the device. The device context is lost when this state is entered, so the Operation System will reinitialize the device when powering it back on. Devices in this state have the longest restore times. All classes of devices define this state.

D2

In general, this state is expected to save more power and preserve less devices context that D1 or D0. Buses in d2 may cause the device to loose some context (i.e. by reducing power on the bus, thus forcing the device to turn off some of its functions). Not all devices will have a D2 state.

D1

In general, this state is expected to save less power and preserve more device context that D2. Not all devices will have a D1 state.

D0

Fully-On: This state is assumed to the highest level of power consumption. The device is complete active and responsive, and is expected to remember all relevant contexts continuously.

Simply put, D3 is considered off while D0 is considered fully on. The D1 and D2 states are not clearly defined except in relation to the other states.

Usage and Configuration

The configuration of the system wide power management is controlled through the Control Panel Power Management. Windows 98 comes with three preset Power Management configurations: Home/Office Desk, Laptop and Personal Server. Customers can create more schemes by using the Save As button. Customers can also set suspend time for Energy Star compliant monitors and the IDE hard drive spin down time. If Windows 98 is reinstalled, the settings are reset to the default.

Power Management Advanced Tab

The Advanced tab will allow the customer to control the System Tray icon, passwords (which is the same as the screen saver password) and to enable the Wake on Ring setting. The Power Buttons settings will allow the choices of Shutdown and Standby modes.

Power Management for Laptops

The dialogs for Power Management for laptop are similar to those for desktop except for the addition of the Alarms and Battery Meter Tabs. The main difference is the customer will be able allowed to change settings based on the computer is running on batteries.

The Alarm Tab will allow the customer to set when an alarm should be triggered and what action to take. The choices of actions are Suspend and Shutdown.

The Battery Meter shows the current sources of power and the percentage remaining. Turning Show Details off will show the total percentage of battery power remaining.

APM in the Device Manager

These settings effect how Windows 98 access with Power Management can be made in the Device Manager. By choosing System Devices Advanced Power Management Support Properties Settings, the customer is able to configure Windows 98 to use APM 1.0 mode (for older power management implementations) and to disable power status polling. Both of these changes should only be made if issues arise using the default settings.

File List

File

Description

ACPI.SYS

Core ACPI Driver

EC.SYS

ACPI embedded controller driver. The controller driver works with the battery driver to regulate the recharging of the battery.

BATTC.SYS

Battery Class driver. The class driver for batteries.

CMBATT.SYS

ACPI Control Method battery driver. This is the minidriver for most batteries.

SMBATT.SYS

SmartBattery driver. The minidriver for a specific type of battery called a SmartBattery. Duracell mainly manufactures Smartbatteries.

POWERCFG.CPL

Power Control Panel

POWRPROF.DLL

Manages policies in the Registry. This file loads twice. Once before the login with default settings and a second time after login with policy settings.

BATMETER.DLL

Systray Battery Meter

Troubleshooting

  1. Discover if the BIOS supports ACPI or APM.
  2. Disable any programs running in the background.
  3. Disable power management in the system’s BIOS.
  4. Force APM 1.0 mode in device manager.
  5. Disable power status polling in device manager.
  6. Check the [BadACPIBios] list in %windir%\inf\machine.inf. If the customer has the same in the listing, check the vendor for an update.

Points to Remember

  • On-Now is an overall power management plan that includes hardware, operating system and application support. However, you must have an ACPI compliant BIOS to make use of this power management.
  • ACPI is a new BIOS specification using the Windows Driver Model that gives power management responsibility to the operation system.
  • ACPI has four power management states and are related to each other in terms of power used versus context retained. The states range from D0 Fully-On assuming the highest level of power consumption to D3 Off: which means power has been fully removed from the device. Power management settings are made in Control Panel - Power Management.
  • In troubleshooting On-Now and ACPI, first thing to ask the customer is "Does the machine support the ACPI specification?" ACPI requires changes in both the BIOS and the chipset on the motherboard for full implementation.