A key component of the OnNow design initiative is a new system board design based on the Advanced Configuration and Power Interface (ACPI) specification. ACPI defines a flexible and abstract hardware interface that enables a wide variety of PC systems to implement power and thermal management functions while still meeting the cost and feature requirements of the target market.
ACPI also provides device configuration and generic system event mechanisms for Plug and Play. ACPI therefore replaces the Plug and Play BIOS and unifies the power management interface with the Plug and Play interface. It also provides support for configurations and resource types that could not be supported before.
ACPI leverages the Plug and Play BIOS data structures while providing an implementation that is independent of the processor architecture and compatible with both Windows 95 and Windows NT.
For OnNow, ACPI enables the operating system to direct power management throughout the PC system, improving integration, increasing effectiveness, and simplifying implementation. System designers have the freedom to implement a wide range of solutions, from the very simple to the very aggressive, while still maintaining full operating system support under both Windows 95 and Windows NT.
Further, power management policies that might be too complicated to implement in hardware or a ROM BIOS can be implemented and supported in the operating system, allowing inexpensive power-managed hardware to support elaborate power management policies.
Finally, ACPI enables investment in power management as a mainstream feature of both PC system hardware and operating systems, while allowing the ongoing independent evolution of each.
This pervasive implementation of power management will enable applications to routinely implement support for these capabilities, introduce new OnNow features, and improve the effectiveness of power management in the PC. Because of the emphasis on convenience and the OnNow goals, and because of the need to enable power management in both Windows 95 and Windows NT, the PC 97 system designs are based on this important new standard.