Not all motherboard devices have an ACPI bus filter.Īll ACPI functionality is transparent to higher-level drivers. Note that Acpi.sys loads an ACPI bus filter only for a device that is described in the ACPI namespace and is permanently connected to the hardware platform (typically, this device is integrated into the core silicon or soldered to the system board). The set of ACPI devices varies from one hardware platform to the next, and depends on the ACPI BIOS and the configuration of the motherboard. For more information, see Device Stacks for an ACPI Device.Ī device for which Acpi.sys creates a device object is called an ACPI device.

Acpi.sys provides power management and PnP features to the device stack by means of these device objects. For other devices described in the ACPI namespace but not on the system board, Acpi.sys creates the PDO. If the device is integrated into the system board, Acpi.sys creates a filter device object, representing an ACPI bus filter, and attaches it to the device stack immediately above the bus driver (PDO). For more information, see ACPI Namespace Hierarchy.įor each device described in the ACPI namespace hierarchy, the Windows ACPI driver, Acpi.sys, creates either a filter device object (filter DO) or a physical device object (PDO). The hardware platform vendor specifies a hierarchy of ACPI namespaces in the ACPI BIOS to describe the hardware topology of the platform. Microsoft ACPI source language (ASL) compiler Other tasks performed by Acpi.sys on a particular hardware platform might include reprogramming the resources for a COM port or enabling the USB controller for system wake-up. Acpi.sys is transparent to the other drivers in the device tree.

Acpi.sys acts as the interface between the operating system and the ACPI BIOS. On hardware platforms that have an ACPI BIOS, the HAL causes Acpi.sys to be loaded during system startup at the base of the device tree.

The responsibilities of Acpi.sys include support for power management and Plug and Play (PnP) device enumeration. The Windows ACPI driver, Acpi.sys, is an inbox component of the Windows operating system.

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