Intel 815 - Manual (Page 147)

Power Delivery
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Intel
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815 Chipset Platform Design Guide 147
12.3.1 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
1. Wake: Pressing the power button wakes the computer from S1–S5.
2. Sleep: Pressing the power button signals software/firmware in the following manner:
a. If SCI is enabled, the power button will generate an SCI to the operating system (OS).
1. The OS will implement the power button policy to allow orderly shutdowns.
2. Do not override this with additional hardware.
b. If SCI is not enabled:
1. Enable the power button to generate an SMI and go directly to soft-off or a
supported sleep state.
2. Poll the power button status bit during POST while SMIs are not loaded and go
directly to soft-off if it gets set.
3. Always install an SMI handler for the power button that operates until ACPI is
enabled.
3. Emergency Override: Pressing the power button for 4 seconds goes directly to S5.
a. This is only to be used in EMERGENCIES when system is not responding.
b. This will cause the user data to be lost in most cases.
4. Do not promote pressing the power button for 4 seconds as the normal mechanism to power
the machine off. This violates ACPI.
5. 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:
a. All lights, except a power state light, must be off.
b. The system must be inaudible: silent or stopped fan, drives off.
Note: Contact Microsoft for the latest information concerning PC9x or PC200x and Microsoft Logo
programs.