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Overview
Version 1.10 12/01/02 2-5
2.2 Firmware Core
This section provides an overview of the services defined by EFI. These include boot services and
runtime services.
2.2.1 EFI Services
The purpose of the EFI interfaces is to define a common boot environment abstraction for use by
loaded EFI images, which include EFI drivers, EFI applications, and EFI OS loaders. The calls are
defined with a full 64-bit interface, so that there is headroom for future growth. The goal of this set
of abstracted platform calls is to allow the platform and OS to evolve and innovate independently of
one another. Also, a standard set of primitive runtime services may be used by operating systems.
Platform interfaces defined in this chapter allow the use of standard Plug and Play Option ROMs as
the underlying implementation methodology for the boot services. The PC industry has a huge
investment in Intel Architecture Option ROM technology, and the obsolescence of this installed
base of technology is not practical in the first generation of EFI-compliant systems. The interfaces
have been designed in such as way as to map back into legacy interfaces. These interfaces have in
no way been burdened with any restrictions inherent to legacy Option ROMs.
The EFI platform interfaces are intended to provide an abstraction between the platform and the OS
that is to boot on the platform. The EFI specification also provides abstraction between diagnostics
or utility programs and the platform; however, it does not attempt to implement a full diagnostic OS
environment. It is envisioned that a small diagnostic OS-like environment can be easily built on
top of an EFI system. Such a diagnostic environment is not described by this specification.
Interfaces added by this specification are divided into the following categories and are detailed later
in this document:
• Runtime services
• Boot services interfaces, with the following subcategories:
Global boot service interfaces
Device handle-based boot service interfaces
Device protocols
Protocol services