Windows 2000 White Paper
server computers that include ACPI system boards. In addition, Plug and Play
device driver support for many device classes is provided by the Microsoft Win32
Driver Model (WDM), which also supports power management and other new
capabilities that can be configured and controlled by the operating system.
To incorporate Plug and Play support into Windows 2000, a native Plug and Play
implementation was integrated into the existing Windows code base. This results in
the following changes for developers who previously created drivers under the
Windows NT 4.0 device driver model:
Bus drivers are now separate from the HAL. Bus drivers control an I/O bus,
including per-slot functionality that is device-independent. In the new
architecture, bus drivers have moved out of the hardware abstraction layer
(HAL) to coordinate with changes and extensions made to existing kernel-mode
components, such as the Executive, device drivers, and the HAL. Bus drivers
are generally provided by Microsoft.
New methods and capabilities are available to support device installation and
configuration. The new design includes changes and extensions to existing
user-mode components, such as the Spooler, class installers, Control Panel
applications, and Setup. In addition, new kernel-mode and user-mode Plug and
Play–enabled components have been added.
New Plug and Play APIs are used to read and write information from the
registry. For the new design, changes and extensions were made to the registry
structure. This structure supports Plug and Play and allows the registry to be
enhanced in future versions of Windows, while also providing backward
Windows 2000 supports legacy Windows NT drivers, but these have no Plug and
Play and power management functionality. Manufacturers who want to support
complete Plug and Play capabilities for their devices and who want the same drivers
to function on both Windows NT and Windows operating systems need to develop
new drivers that integrate the latest Plug and Play and power management
This white paper provides a brief overview of the architecture and design direction
for Plug and Play under Windows 2000. The beta releases of the Windows 2000
DDK document the actual driver modifications required to allow current drivers to
work in a Windows 2000 Plug and Play system.