Overview
ACPI aims to consolidate, check and improve upon existing power and configuration standards for hardware devices. It provides a transition from earlier standards to entirely ACPI-compliant hardware, with some ACPI operating systems already removing support for legacy hardware. With the intention of replacing Advanced Power Management, the MultiProcessor Specification and the Plug and Play BIOS Specification, the standard brings power management under the control of the operating system (OSPM), as opposed to the previous BIOS-central system, which relied on platform-specific firmware to determine power management and configuration policy.
The ACPI specification contains numerous related components for hardware and software programming, as well as a unified standard for device/power interaction and for bus configuration. Linus Torvalds, creator of the Linux kernel, once described it as "a complete design disaster in every way" in relation to his view that "modern PCs are horrible". Some software developers have trouble implementing ACPI, and express concerns about the requirements that bytecode from an external source must be run by the system with full privileges.
Microsoft's Windows 98 became the first operating system with full support for ACPI, with Windows 2000, Windows XP, Windows Vista, Windows 7, eComStation, FreeBSD, NetBSD, OpenBSD, HP-UX, OpenVMS, Linux, and PC versions of SunOS all having at least some support for ACPI.
Read more about this topic: Advanced Configuration And Power Interface