Specifications

Intel
®
810E2 Chipset Platform
R
Design Guide
151
6.4.1. Power Button Implementation
The following items should be considered when implementing a power management model for a desktop
system. The power states are as follows:
S1 – Stop Grant – (processor context not lost)
S3 – STR (Suspend to RAM)
S4 – STD (Suspend to Disk)
S5 – Soft-off
• Wake: Pressing the power button wakes the computer from S1–S5.
• Sleep: Pressing the power button signals software/firmware in the following manner:
• If SCI is enabled, the power button will generate an SCI to the OS.
 The OS will implement the power button policy to allow orderly shutdowns.
 Do not override this with additional hardware.
• If SCI is not enabled:
 Enable the power button to generate an SMI and go directly to soft-off or a supported sleep
state.
 Poll the power button status bit during POST while SMIs are not loaded and go directly to soft-
off if it gets set.
 Always install an SMI handler for the power button that operates until ACPI is enabled.
• Emergency Override: Pressing the power button for 4 seconds goes directly to S5.
 This is only to be used in EMERGENCIES when the system is not responding.
 This will cause the user data to be lost in most cases.
• Do not promote pressing the power button for 4 seconds as the normal mechanism to power the
machine off. This violates ACPI.
• To be compliant with the latest PC9x specification, machines must appear to the user to be off when
in the S1–S4 sleeping states. This includes:
 All lights, except a power state light, must be off.
 The system must be inaudible: silent or stopped fan, drives off.
• Note: Contact Microsoft* for the latest information concerning PC9x and Microsoft* Logo
programs.