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Version 1.10 12/01/02 2-1
2
Overview
EFI allows the extension of platform firmware by loading EFI driver and EFI application images.
When EFI drivers and EFI applications are loaded they have access to all EFI defined runtime and
boot services. See Figure 2-1.
OM13144
Standard
firmware
platform
initilization
Drivers and
applications
loaded
iteratively
Boot from
ordered list
of EFIOS
loaders
Operation
handed off
to OS loader
API specified Value add implementation
Boot Manager EFI binaries
Platform
Init
EFI Image
Load
EFI
OS Loader
Load
Boot
Services
Terminate
EFI
Driver
EFI
Application
EFI
Bootcode
OS Loader
EFI API
Retry
Failure
Figure 2-1. Booting Sequence
EFI allows the consolidation of boot menus from the OS loader and platform firmware into a single
platform firmware menu. These platform firmware menus will allow the selection of any EFI OS
loader from any partition on any boot medium that is supported by EFI boot services. An EFI OS
loader can support multiple options that can appear on the user interface. It is also possible to
include legacy boot options, such as booting from the A: or C: drive in the platform firmware
boot menus.
EFI supports booting from media that contain an EFI OS loader or an EFI-defined System Partition.
An EFI-defined System Partition is required by EFI to boot from a block device. EFI does not
require any change to the first sector of a partition, so it is possible to build media that will boot on
both legacy Intel architecture and EFI platforms.