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Intel® Server Board SE7320SP2 & Intel Server Board SE7525GP2 TPS System BIOS
Revision 2.0
98
home/office environments has different requirements than one used for enterprise applications.
The BIOS supports HDG 3.0.
4.9.2 Advanced Configuration and Power Interface (ACPI)
The BIOS is ACPI 2.0c compliant. The primary role of the BIOS is to provide ACPI tables.
During POST, the BIOS creates the ACPI tables and locates them in extended memory (above
1MB). The location of these tables is conveyed to the ACPI-aware operating system through a
series of tables located throughout memory. The format and location of these tables is
documented in the publicly available ACPI specification.
To prevent conflicts with a non-ACPI-aware operating system, the memory used for the ACPI
tables is marked as “reserved” in the INT 15h, function E820h.
As described in the ACPI specification, an ACPI-aware operating system generates an SMI to
request that the system be switched into ACPI mode. The BIOS responds by setting up all
system (chipset) specific configuration required to support ACPI, and sets the SCI_EN bit as
defined by the ACPI specification. The system automatically returns to legacy mode on hard
reset or power-on reset.
There are three runtime components to ACPI:
• ACPI Tables: These tables describe the interfaces to the hardware. ACPI tables can
make use of a p-code type of language, the interpretation of which is performed by the
operating system. The operating system contains and uses an ACPI Machine Language
(AML) interpreter that executes procedures encoded in AML and stored in the ACPI
tables. AML is a compact, tokenized, abstract machine language. The tables contain
information about power management capabilities of the system, APICs, and bus
structure. The tables also describe control methods that operating systems can use to
change PCI interrupt routing, control legacy devices in Super I/O, find out the cause of
wake events, and handle PCI hot plugging, if applicable.
• ACPI Registers: The constrained part of the hardware interface, described (at least in
location) by the ACPI tables.
• ACPI BIOS: This is the code that boots the machine and implements interfaces for
sleep, wake, and some restart operations. The ACPI Description Tables are also
provided by the ACPI BIOS.
The BIOS supports S0, S1, S4, and S5 states. S1 and S4 are considered sleep states. The
ACPI specification defines the sleep states and requires the system to support at least one of
them.
While entering the S4 state, the operating system saves the context to the disk and most of the
system is powered off. The system can wake on a power button press, or a signal received from
a wake-on-LAN compliant LAN card (or onboard LAN), modem ring, PCI power management
interrupt, or RTC alarm. The BIOS performs complete POST upon wake up from S4, and
initializes the platform.
The system can wake from the S1 state using a PS/2 keyboard, mouse, or USB device, in
addition to the sources described above.
The wake-up sources are enabled by the ACPI operating systems with cooperation from the
drivers; the BIOS has no direct control over the wakeup sources when an ACPI operating