2.0 System BIOS Initialization

The Power On Self Test (POST) procedure of a system BIOS is designed to identify, test, and configure the system in preparation for starting the operating system. At the completion of POST, the PC compatible system BIOS attempts to have all of the appropriate devices enabled in order for them to be properly recognized and functioning when the operating system loads.

Over the years, PC compatible systems have become much more sophisticated in terms of the bus architectures supported and the devices attached. As these PC compatible systems have evolved and become more sophisticated, so has the system BIOS, which is responsible for the initial configuration of these devices. However, one component has remained relatively constant in a PC compatible system. This is the system resources. System resources, as described in this document include DMA channels, Interrupt Request Lines (IRQs), I/O addresses, and memory.

As the sophistication of these systems increases with more and more devices, the possibility of resource conflicts also increase, leading to a possible boot or system failure. The Plug and Play BIOS specification is defined to solve the problems that occur with resource conflicts. Specifically, the Plug and Play BIOS is taking on a new responsibility to ensure that the operating system is loaded with a conflict free set of resources, as well as indicating to the operating system the resources that are currently used by systemboard devices.