1.0 Overview
This Plug and Play BIOS Specification defines new functionality to be provided in a PC compatible system BIOS to fulfill the goals of Plug and Play. To achieve these goals, several new components have been added to the System BIOS. Two key areas that are addressed by the System BIOS are resource management and runtime configuration.
Resource management provides the ability to manage the fundamental system resources which include DMA, Interrupt Request Lines (IRQs), I/O and Memory addresses. These resources, termed system resources, are in high demand and commonly are over-allocated or allocated in a conflicting manner in ISA systems, leading to bootstrap and system configuration failures. A plug and play system BIOS will play a vital role in helping to manage these resources and ensure a successful launch of the operating system.
In its role as resource manager, a Plug and Play BIOS takes on the responsibility for configuring Plug and Play cards, as well as systemboard devices during the power-up phase. After the POST process is complete, control of the Plug and Play device configuration passes from the system BIOS to the system software. The BIOS does, however, provide configuration services for systemboard devices even after the POST process is complete. These services are known as Runtime Services.
Runtime configuration is a concept that has not previously existed in a System BIOS before. The system BIOS has not previously provided the ability to dynamically change the resources allocated to systemboard devices after the operating system has been loaded. The Plug and Play BIOS Specification provides a mechanism whereby a Plug and Play operating system may perform this resource allocation dynamically at runtime. The operating system may directly manipulate the configuration of devices which have traditionally been considered static via a System BIOS device node structure.
In addition, a Plug and Play System BIOS may also support event management. By means of the interfaces outlined in this document, the System BIOS may communicate the insertion and removal of newly installed devices which have been added to the system at runtime. The event management support defined by this specification are specific to devices controlled by the system BIOS, such as docking a notebook system to, or undocking it from, an expansion base. This event management does not encompass the insertion and removal of devices on the various expansion busses.
This document describes the BIOS support necessary for both systemboards and add-in boards with Option ROMs.