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Appendix C
Utilities
Extensible Firmware Interface Boot Manager
162
Extensible Firmware Interface Boot Manager
Extensible Firmware Interface (EFI) is an OS and platform-independent boot and pre-boot interface. EFI
resides between the OS and platform firmware. This allows the OS to boot without having details about the
underlying hardware and firmware. EFI supports boot devices; uses a flat memory model; and hides platform
and firmware details from the OS.
NOTE EFI and Pre-OS System Environment (POSSE) are similar. EFI is an Intel specification,
whereas POSSE is the HP implementation that aids HP support.
EFI consolidates boot utilities similar to those found in PA-RISC based servers, such as the Boot Console
Handler (BCH), and platform firmware into a single platform firmware. EFI allows the selection of any EFI
OS loader from any boot medium that is supported by EFI boot services. An EFI OS loader supports multiple
options on the user interface.
EFI supports booting from media that contain an EFI OS loader or an EFI-defined server partition. An
EFI-defined server partition is required by EFI to boot from a block device.
Figure C-1 EFI Boot Sequence
EFI
Driver
EFI
Application
EFI
Bootcode
OS Loader
Retry
Failure
EFI API
Platform
Init
EFI Image
Load
EFI
OS Loader
Load
Boot Services
Terminate
Standard
firmware
platform
initialization
Drivers and
application
loaded
iteratively
Boot from
ordered list
of EFI OS
loaders
Operation
handed off to
OS Loader
Application Program
Interface (API) specified
Value add implementation
Boot manager EFI transfers