Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel
®
Pentium
®
4 Processor-M and Intel
®
845MP/845MZ Chipset Platform
Design Guide 159
R
11. Platform Power Guidelines
11.1. Definitions
Suspend-To-RAM (STR):
In the STR state, the system state is stored in main memory and all unnecessary systemlogic is turned off.
Only main memory and logic required to
wake the system remain powered.
Full-power operation:
During full-power operation, all components on the motherboard remain powered. Note that full-power
operation includes both
the full-on operating state and the S1 (PROCESSOR stop-grant state) state.
Suspend operation:
During suspend operation, power is removed from some components on the motherboard. The customer
reference board supports two suspend states: Suspend-to-RAM (S3) and Soft-off (S5).
Core power rail:
A power rail that is only on during full-power operation. These power rails are on when the PSON signal
is asserted to the ATX power supply.
Standby power rail:
A power rail that in on during suspend operation (these rails are also on during full-power operation).
These rails are on at all times (when the power supply is plugged into AC power). The only standby
power rail that is distributed
directly from the ATX power supply is: 5 V
SB
(5 V Standby). There are
other standby rails that are created with voltage regulators on the motherboard.
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 5V
SB
using a
voltage regulator.
Dual power rail:
A dual power rail is derived from different rails at different times (depending on the power state of the
system). Usually, a dual power rail is derived from a
standby supply during suspend operation and
derived from a
core supply during full-power operation. Note that the voltage on a dual power rail may
be misleading.