Design Guide

Intel 855GM/GME Chipset Based System Power Delivery Guidelines
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Intel
®
855GM/855GME Chipset Platform Design Guide 255
13. Intel 855GM/GME Chipset Based
System Power Delivery Guidelines
13.1. Definitions
Table 108. Power Delivery Definitions
Term Definition
S0/Full-On operation: During S0 operation, all components on the motherboard are powered and the system is
fully functional.
S1-M/Power-On-
Suspend (POS, Mobile):
In the mobile implementation of the Power-On-Suspend state, the outputs of the clock
chip are stopped in order to save power. All components remain powered but may or may
not be in a low power state.
S3/Suspend-To-RAM
(STR):
In the S3 state, the system state is stored in main memory and all unnecessary system
logic is turned off. Only main memory and logic required to wake the system remain
powered.
S4/Suspend-To-Disk
(STD):
In the S4 state, the system state is stored in non-volatile secondary storage (e.g. a hard
disk) and all unnecessary system logic is turned off. Only logic required to wake the
system remain powered. Standby power rails may or may not be powered depending on
system design and the presence of AC or battery power.
S5/Soft-Off: The S5 state corresponds to the G2 state. Restart is only possible with the power button.
Full-Power operation: During Full-Power operation, all components remain powered. Full-power operation
includes both S0 and the S1M (CPU Stop-Grant state).
Suspend operation: 855GM/GME chipset-based systems can be designed to support a number of suspend
states such as Power-On-Suspend (S1M), Suspend-to-RAM (S3), Suspend-to-Disk (S4),
and Soft-Off (S5). During suspend operation, with exception of S1M, power is removed
from some components on the motherboard.
Core power rail: A power rail that is only on during full-power operation.
Standby power rail: A power rail that is on during a suspend operation (S3, S4 or S5). The rail is also on
during full-power operation.
Derived power rail: A derived power rail is any power rail that is generated from another power rail using an
on-board voltage regulator. For example, 3.3 V
SB
is usually derived (on the motherboard)
from 5 V
SB
using a voltage regulator.
13.2. Platform Power Requirements
The following figure shows the power delivery architecture for an example of the Intel 855GM/GME
chipset based system. To ensure that enough power is available during S3, a thorough power budget
should be completed. The power requirements should include each device’s power requirements, both in
suspend and in Full-On. The power requirements should be compared against the power budget supplied
by the power supply.