Bios; Overview; Supported Acpi States; Power Management - Dell PowerEdge R820 Technical Manual

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9 BIOS

9.1 Overview

The PowerEdge T110 II BIOS supports ACPI and power management features.

9.2 Supported ACPI States

The PowerEdge T110 II BIOS is compliant with ACPI version 2.0a.
9.2.1

Power Management

Power management features come in two types: fixed or generic. Fixed features use bits defined in
the ACPI specification for specific capabilities. The fixed feature bits give the OS complete control
over the power management of a device, since the location of the bits is given to the OS in the FACP
table. Thus, a driver can directly access bits to control a device's power management. Generic
features have defined enable and status bits, but the functionality is not fully visible to the OS. Dell
provides ASL code to handle the details of generic features, allowing the OS to intelligently
communicate with system-specific hardware.
Table 10 summarizes the power management features on this system:
Feature
ACPI Mode Switch
Sleep States
Power Button
Real-Time Clock
Power Mgmt.
Timer
Power Mgmt. Event
(PME)
PowerEdge T110 II Technical Guide
Table 10.

Power Management Features

Type
Fixed
Fixed
Fixed
Fixed
Fixed
Generic
Enable/Status/
Ctrl bit location
PCH
PCH
PCH
PCH
PCH
PCH
Description
The OS uses the SCI_EN bit in
PCH to switch from legacy
mode to ACPI mode.
Supported states: S0
(Working), S4-OS
(‗Hibernation'), and S5 (Soft-
off).
S1 (also called standby or
suspend) and S3 are not
supported.
In ACPI mode, OS has control
of the power button. In non-
ACPI mode, SMI handler owns
power button events.
The OS is able to configure the
system to wake on the RTC
alarm.
PCH 32-bit power management
timer is used
When a device signals PME, the
system wakes (if necessary),
the OS detects the event, and
a Dell-defined ASL routine
handles the event. Wake-on-
LAN is one example of a PME.
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