Intel SE7501WV2 manual Advanced Configuration and Power Interface Acpi

Intel® Server Board SE7501WV2 TPS BIOS

6.12.2Advanced Configuration and Power Interface (ACPI)

The primary role of the ACPI BIOS is to supply the ACPI Tables. POST creates the ACPI Tables and locates them above 1 MB in extended memory. 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, issues the appropriate command to the BMC to enable ACPI mode 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 AML (ACPI Machine Language) interpreter that executes procedures encoded in AML and stored in the ACPI Tables; ACPI Machine Language is a compact, tokenized, abstract machine language. The tables contain information about power management capabilities of the system, APICs, and the bus structure. The tables also describe control methods that the operating system uses to change PCI interrupt routing, control legacy devices in Super I/O, and find the cause of wake events.

•ACPI Registers: ACPI registers are the constrained part of the hardware interface, described (at least in location) by the ACPI Tables.

•ACPI BIOS: This code boots the machine and implements interfaces for sleep, wake, and some restart operations. The ACPI BIOS also provides the ACPI Description Tables.

All IA-32 server platforms support S0, S4, and S5 states. The SE7501WV2 server board also supports the S1 state. 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 from such a state on various inputs depending on the hardware. The SE7501WV2 platform will wake on a power button press, or a signal received from a wake-on-LAN compliant LAN card (or on-board LAN), modem ring, PCI power management interrupt, or RTC alarm. The BIOS performs a complete POST upon a wake from S4 and initializes the platform. S4BIOS is not supported.

The SE7501WV2 server board can wake from the S1 state using a PS/2 keyboard, mouse, and USB device in addition to the sources described above.

The wake sources are enabled by the ACPI operating systems with co-operation from the drivers; the BIOS has no direct control over the wake sources when an ACPI operating system is loaded. The role of the BIOS is limited to describing the wake sources to the operating system and controlling secondary control/status bits via a Differentiated System Description Table (DSDT).

Revision 1.0	79
	Intel reference number C25653-001