Supported Acpi States; Power Management Modes; Dell Active Power Controller; Power Saving Bios Setting (Os Control) - Dell PowerEdge R415 Technical Manual

Dell

8.2 Supported ACPI States

The following ACPI states are supported:

ACPI compliance: S0, S4, S5

NO S1, S2, S3 (STR)
State S4 is supported by OS support only.

8.3 Power Management Modes

8.3.1 Dell Active Power Controller

The Dell Active Power Controller (DAPC) is implemented in system BIOS and uses hardware level counters,
etc., to determine hardware utilization. The BIOS uses this information to determine when to change the
processor's operating frequency. The DAPC is OS independent and means that the OS no longer has control.
This provides a consistent power management solution regardless of the installed OS. Some OS(s),
particularly hypervisors, do not support power management, thus DAPC provides a solution when there
otherwise would not be one.

8.3.2 Power Saving BIOS Setting (OS Control)

With the Power Saving BIOS setting, the OS monitors process/thread level utilization of the processor and
uses processor controls to change the processor's operating frequency. For heavy workloads, the OS will run
the processor at higher frequencies for additional performance. Lighter workloads do not need high
performance, thus the OS will run the processor at lower frequencies.

8.3.3 Maximum Performance

The Maximum Performance mode disables power management. In this mode, the processor frequency is
statically set to the highest supported frequency.
The power management features are implemented via two categories: 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 12 summarizes power management features, and Table 13 describes
the possible power profiles.
Feature Type
ACPI Mode Fixed
Switch
Sleep States Fixed
Power Button Fixed
PowerEdge R415 Technical Guide

BIOS Power Management Features

Table 12.
Enable/Status/ Description
Ctrl bit
location
PCH The OS uses the SCI_EN bit to switch from legacy mode to
ACPI mode.
PCH Supported states: S0 (Working), S4-OS (Hibernation in
Microsoft
Not supported: S1 (standby or suspend) and S3.
PCH In ACPI mode, OS has control of the power button. In non-
® ®
Windows 2000), and S5 (soft-off).
34