Windows 98 does not provide support for Passive Cooling Mode as described in the Advanced Configuration and Power Interface (ACPI) specification. Windows 98 only supports Active Cooling Mode.

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The ACPI specification defines two categories of methods for cooling computer systems:

•	Active cooling methods
•	Passive cooling methods

Active cooling methods may include turning on one or more fans to provide increased airflow and improve dissipation of heat from active components. these methods cool the computer without decreasing its performance, but increase power consumption and often increase noise production.

Passive cooling methods may include slowing down (throttling) the computer's central processing unit (CPU) so that the CPU generates less heat. These methods tend to decrease power consumption, but decrease overall system performance when used.

A computer which complies with the ACPI specification may operate in one of two cooling modes:

•	Active Cooling mode
•	Passive Cooling mode

In Active Cooling mode, the computer first uses active cooling methods to control the temperature of the computer. If the computer's temperature continues to rise when the active cooling methods are in use, then the computer uses passive cooling methods to cool overheated components.

In Passive Cooling mode, the computer first uses passive cooling methods to control the temperature of the computer. If the computer's temperature continues to rise when the passive cooling methods are in use, then the computer uses active cooling methods to cool overheated components.

In either cooling mode, if the temperature continues to rise to critical levels, the computer may shut down or go to some other non-operating, lower-power state. This is to help prevent thermal damage to components.

The computer's cooling mode is controlled by the temperature set point. This is the temperature at which each cooling method is activated. For example, if the set point for the active cooling method is a lower temperature than the set point for the passive cooling method, then the active method is employed first, and the computer goes to Active Cooling mode. If the set point for the passive cooling method is lower than the set point for the active cooling method, then the passive method is employed first, and the computer goes to Passive Cooling mode.

Windows 98 configures the computer to operate only in Active Cooling mode, and does not provide an interface for changing the active and passive cooling set points so that the computer could be reconfigured to operate in Passive Cooling mode.

For more information, please see the following article in the Microsoft Knowledge Base:

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Information on ACPI specifications and implementation can be found at the following Internet location:

The third-party contact information included in this article is provided to help you find the technical support you need. This contact information is subject to change without notice. Microsoft in no way guarantees the accuracy of this third-party contact information.

Active and passive cooling methods and modes are discussed in the ACPI specification, Revision 1.0, December 22, 1996, in section 12, "Thermal Management".

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