Power Management Features - Contec PC-686(CPCI)-LV User Manual

1.5

Power Management Features

1.5.1. Overview
The PIIX4 power management function provides a wide range of
capabilities and configuration options allowing a system designer to implement a
wide range of power saving modes.
PIIX4 provides for four main areas of power management:
- Clock Control and Processor Complex Management
- Peripheral Device Management
- System Management (SMI Generation, System Management Bus)
- System Suspend and Resume
Brief descriptions of primary power management function follow.
Clock Control: When the operating system, application program, or system software
is not performing useful work, the processor complex (Processor, Host Bridge, DRAM,
L2 cache) does not need to be executing cycles and, therefore, can be placed in Standby
mode.
Peripheral Device Management: Peripheral device resources are monitored to
detect when a specific device is idle. PIIX4 then informs system power management
software, which can place that individual device into a power managed condition (such
as Local Standby or Powered Off). Accesses targeting that device are then monitored.
System Suspend: Once the power management software has determined that the
system is fully idle or that a critical system event has occurred, it can place the system
into a suspend state, which allows for increased power savings. The software
configured PIIX4 for the types of suspend, types of resume or wake-up events, and the
PIIX4 automatically transitions the system into suspend. When an enabled resume
event is detected, PIIX4 automatically restores the system operation.
- Three suspend states
PC-686 (CPCI)-LV User's Manual
CHAPTER 1 – Introduction
7