HP Power Regulator for ProLiant servers

• HP Static Low Power mode

• HP Dynamic Power Savings mode

• OS Control mode

Figure 1 shows the methods for controlling P-states in the multiple Power Regulator operating modes.

HP has developed server ROM firmware that implements the Static High and Low modes, Dynamic

Power Saving mode, and OS mode. Upgrades to the OS or application do not affect Power

Regulator. The ROM firmware or the OS with a processor driver directly control processor P-states.

Figure 1. Methods for controlling processor P-states

• Dynamic Power Saving

mode

• Static High mode

• Static Low mode

Hardware

Registers

System ROM

OS Control mode

Hardware

Registers

Driver

Dynamic Power Saving

mode with Collaborative

Power Control

Hardware

Registers

System ROM

Driver

Figure 1 also shows the new Collaborative Power Control (CPC) mode (described later in the paper),

a capability that lets the Power Regulator control P-states by using both system ROM firmware and OS

power management capabilities together. Operating systems supporting CPC can communicate with

the System ROM and collaborate on performance state changes. Unlike OS Control mode, CPC

ensures that the HP System ROM and OS actively manage power, regardless of whether the OS

supports power management features.

Processor drivers

Processor drivers (shown in Figure 1) enable the OS Control mode and Collaborative Power Control

mode. Processor drivers used in Microsoft Windows® operating systems provide an abstraction layer

between specific processor designs and the OS. Windows uses information obtained from the CPU

Identification instruction to determine processor type and feature set in order to load the correct

processor driver.

HP Static High Performance mode

The system’s processors operate continuously at the highest power and performance state (Pmax) in

Static High Performance mode. Neither the system’s firmware nor the OS will ever program the

processors to run in a lower power or performance state. This mode is important for applications in

which performance is critical and power consumption is less important.

HP Static Low Power mode

The system’s processors operate continuously at the lowest power and performance state (Pmin) in

Static Low Power mode. This mode is useful for environments where power availability is constrained

and it is critical to lower the server’s maximum power use.