Intel Extensible Firmware Interface, Specification

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Introduction
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Compatibility by design . The design of the system partition structures also preserves all the
structures that are currently used in the “PC-AT” boot environment. Thus it is a simple matter
to construct a single system that is capable of booting a legacy OS or an EFI-aware OS from
the same disk.
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Simplifies addition of OS-neutral platform value-add . The specification defines an open
extensible interface that lends itself to the creation of platform “drivers.” These may be
analogous to OS drivers, providing support for new device types during the boot process, or
they may be used to implement enhanced platform capabilities like fault tolerance or security.
Furthermore this ability to extend platform capability is designed into the specification from the
outset. This is intended to help developers avoid many of the frustrations inherent in trying to
squeeze new code into the traditional BIOS environment. As a result of the inclusion of
interfaces to add new protocols, OEMs or firmware developers have an infrastructure to add
capability to the platform in a modular way. Such drivers may potentially be implemented
using high level coding languages because of the calling conventions and environment defined
in the specification. This in turn may help to reduce the difficulty and cost of innovation. The
option of a system partition provides an alternative to non-volatile memory storage for such
extensions.
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Built on existing investment . Where possible, the specification avoids redefining interfaces and
structures in areas where existing industry specifications provide adequate coverage. For
example, the ACPI specification provides the OS with all the information necessary to discover
and configure platform resources. Again, this philosophical choice for the design of the
specification is intended to keep barriers to its adoption as low as possible.
1.3 Target Audience
This document is intended for the following readers:
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OEMs who will be creating Intel architecture-based platforms intended to boot shrink-wrap
operating systems.
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BIOS developers, either those who create general-purpose BIOS and other firmware products
or those who modify these products for use in Intel architecture-based products.
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Operating system developers who will be adapting their shrink-wrap operating system products
to run on Intel architecture-based platforms.