Книга: Writing Windows WDM Device Drivers

ACPI, OnNow, and Plug and Play

ACPI, OnNow, and Plug and Play

New PCs aim to use less power and switch on more quickly, as well as supporting Plug and Play. Windows and new BIOS chips use the Advanced Configuration and Power Interface (ACPI) specification to help with these tasks.

ACPI-based hardware knows how to turn off or reduce power to some devices. Windows drivers can now help in this process by using the Power Management IRPs and routines, and the power management routines that are relevant for its device class. The aim of the OnNow initiative is that a PC may appear to be off, when in fact it is just "sleeping", waiting for a soft power on button to be pressed. As the operating system and drivers are already loaded into memory, it takes less time to start up the system. Devices simply need to be powered up for the user to get started. A remote control handset or incoming modem call may similarly be used to wake the system up.

Both Windows 98 and Windows 2000 can now take full use of the Plug and Play hardware facilities to allow easy device insertion and removal. Again, drivers need to help in this process, allocating and releasing resources only as instructed by the Plug and Play Manager.

PC 99 specifies that ACPI, OnNow, and Plug and Play must be supported.:

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