Plug and Play BIOS Specification

Plug and Play BIOS Specification 1.0A Page 6
Hardware and Operating System independence
The extensions to the system BIOS isolate the systemboard hardware through well defined
interfaces and structures. The system device nodes represent devices that are controlled by the
system BIOS. The operating system requires no specific knowledge of the systemboard in order to
control these devices, and instead relies on the system BIOS to isolate it from the underlying
hardware.
1.2 Enhancements to the current BIOS architecture
The Plug and Play BIOS Specification attempts to make several improvements to the current PC system
BIOS architecture to achieve the goals stated previously.
•• Perform resource allocation and conflict resolution at POST time.
The current System BIOS Architecture performs no such resource management at POST time. The
goal is to increase the probability of successfully bootstrapping into the OS by specifying resource
management at POST time.
•• Actively monitor the INT 19h bootstrap vector
The current System BIOS Architecture allows option ROMs to hook INT 19h indiscriminately. By
actively monitoring control of INT 19h, the System BIOS may regain control of the Bootstrap
process to ensure that the Operating System is loaded from the proper device and in the proper
manner.
•• Provide a mechanism for Remote Program Load
The current architecture provides no specific support for RPL. Consequently, RPL devices must
resort to hooking the INT 19h bootstrap vector or INT 18h, the alternate bootstrap vector. Hooking
these vectors can interfere with system specific security features, as well as result in bootstrap
failures. The method and support for booting from RPL devices is beyond the scope of the Plug
and Play BIOS Specification. A separate specification should define explicit support for RPL
devices.
•• Provide Runtime Configuration Support
Proprietary techniques exist to support device resource configuration and reporting. The Plug and
Play BIOS Specification defines specific, standard interfaces whereby configuration software may
identify and configure devices on the systemboard.
•• Provide Dynamic Event Notification
A further extension of the Runtime Configuration Support allows the System BIOS to report
dynamic configuration events to the Plug and Play software such that new devices added into the
system may be resource managed. This dynamic event notification interface is specific to devices
controlled by the system BIOS. It does not encompass the insertion and removal of devices on the
various expansion busses