Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 871

Firmware Overview
Itanium-based systems make use of several firmware components: Processor
Abstraction Layer (PAL), System Abstraction Layer (SAL), Unified Extensible Firmware
Interface (UEFI) and Advanced Configuration and Power Interface (ACPI).
The PAL and SAL components work together to handle the reset abort event. The reset
abort handling performs processor and system initialization for operating system (OS)
boot and provides an API to the operating system loader. The PAL and SAL firmware
layers work together to handle machine check aborts (MCA), initialization events
(INIT), and platform management interrupt (PMI) handling. All firmware components
also provide runtime procedure calls to abstract processor and platform functions that
may vary across implementations.
This chapter will provide an overview of the firmware components and how the
firmware components interact with each other as well as with the operating system. For
the full architecture specifications of the PAL firmware please refer to
"Processor Abstraction Layer."
firmware components please refer to
The PAL layer is developed by Intel Corporation and delivered with the processor. The
SAL, UEFI and ACPI firmware is developed by the platform manufacturer and provide a
means of supporting value added platform features from different vendors.
The interaction of the various functional firmware blocks with the processor, platform
and operating system is shown in
13.1 Processor Boot Flow Overview
13.1.1 Firmware Boot Flow
Upon detection of a reset event on a processor based on the Itanium architecture,
execution begins at an architected entry point inside of PAL. This PAL code will verify
the integrity of the PAL code and may perform some basic processor testing. PAL will
then branch to an entry point within the SAL firmware. This first branch to SAL is to
determine if a firmware update is needed requiring re-programming of the firmware
code. If no firmware update is needed SAL will branch back to PAL.
PAL now performs additional processor testing and initialization. These first processor
tests are performed without platform memory. PAL indicates the outcome of the testing
and branches to an entry point within SAL firmware for the second time. SAL will now
begin platform testing and initialization. The exact division of work between SAL and
UEFI from that point on is platform implementation dependent. It is required that the
SAL runtime services, the UEFI boot and runtime services, and the ACPI tables and
control methods be exposed to the operating systems for correct operation.
Volume 2, Part 2: Firmware Overview
For full architecture specifications on SAL, UEFI and ACPI
Section 1.2, "Related Documents" on page
Figure 13-1, "Firmware Model" on page
13
Chapter 11,
2:505.
2:624.
2:623