Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 535

At a minimum, all of the PAL firmware components, pointers at the top of the firmware
address space, FIT tables and the portion of the SAL code that is executed at the
RECOVERY CHECK hand-off must be accessible from the processor without any special
system fabric initialization sequence. This implies that the system fabric is implicitly
initialized at power on for accessing the portions of the firmware address space listed
above or that the special hardware which contains the firmware code and data is
implemented on the processor and not accessed across the system fabric. The entire
firmware code and data area can also be implicitly initialized at power on from the
processor as well, but the minimum set is listed above.
The Firmware Interface Table (FIT) contains starting addresses and sizes for the
different firmware components. Because these code blocks may be compiled at
different times and places, code in one block (such as PAL_A) cannot branch to code in
another block (such as PAL_B) directly. The FIT allows code in one block to find
entrypoints in another.
Figure 11-5.
4GB-X
4GB-(X+Y)
Each FIT entry contains information for the corresponding firmware component. The
first entry contains size and checksum information for the FIT itself. The order of the
following FIT entries must be arranged in ascending order by the type field, otherwise
execution of firmware code will be unpredictable. Multiple FIT entries of the same type
are allowed as shown in
When multiple entries of the same type exist for PAL components, PAL searches the FIT
table in ascending order looking for the first entry that is compatible and error free for
the processor it is currently executing on.
Volume 2, Part 1: Processor Abstraction Layer
Figure 11-5 below shows the FIT layout.
Firmware Interface Table
OEM use
OEM use
Processor-specific PAL_A (other entries are optional)
Processor-specific PAL_A (one entry is required for the split PAL_A model)
PAL_B entry (other entries are optional)
PAL_B entry (one entry is required)
FIT header
Figure 11-5.
(16 bytes)
(16 bytes)
(16 bytes)
Y
(16 bytes)
(16 bytes)
(16 bytes)
(16 bytes)
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