Dell PowerEdge R415 Technical Manual

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Dell34PowerEdge R415 Technical Guide8.2 Supported ACPI StatesThe 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 Modes8.3.1 Dell Active Power ControllerThe 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 theprocessor’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 thereotherwise 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 anduses processor controls to change the processor’s operating frequency. For heavy workloads, the OS will runthe processor at higher frequencies for additional performance. Lighter workloads do not need highperformance, thus the OS will run the processor at lower frequencies.8.3.3 Maximum PerformanceThe Maximum Performance mode disables power management. In this mode, the processor frequency isstatically 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 givethe OS complete control over the power management of a device, since the location of the bits is given tothe 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. Dellprovides ASL code to handle the details of generic features, allowing the OS to intelligently communicatewith system-specific hardware. Table 12 summarizes power management features, and Table 13 describesthe possible power profiles.Table 12. BIOS Power Management FeaturesFeature Type Enable/Status/Ctrl bitlocationDescriptionACPI ModeSwitchFixed PCH The OS uses the SCI_EN bit to switch from legacy mode toACPI mode.Sleep States Fixed PCH Supported states: S0 (Working), S4-OS (Hibernation inMicrosoft® Windows® 2000), and S5 (soft-off).Not supported: S1 (standby or suspend) and S3.Power Button Fixed PCH In ACPI mode, OS has control of the power button. In non-