Power Delivery; Terminology And Definitions - Intel VC820 - Desktop Board Motherboard Design Manual

System Design Considerations
6.1

Power Delivery

6.1.1

Terminology and Definitions

Term
Suspend-To-
RAM (STR)
Full-power
operation
Suspend
operation
Power rails
Core power rail A power rail that is only on during full-power operation. These power rails are
Standby power
rail
Derived power
rail
Dual power rail A dual power rail is derived from different rails at different times (depending on
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Intel 820 Chipset Design Guide
Definition
In the STR 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. This state is used in the Reference Board (refer to
Appendix A, "Reference Design Schematics: Uni-Processor"
"Reference Design Schematics:
management state.
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 (CPU stop-grant state) state.
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).
An ATX power supply has 6 power rails: +5V, -5V, +12V, -12V, +3.3V, 5VSB.
In addition to these power rails, several other power rails are created with
voltage regulators on the Intel
on when the PSON signal is asserted to the ATX power supply. The core power
rails that are distributed directly from the ATX power supply are: ±5V, ±12V
and +3.3V.
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: 5VSB (5V Standby). There are other standby
rails that are created with voltage regulators on the motherboard.
A derived power rail is any power rail that is generated from another power rail
using an on-board voltage regulator. For example, 3.3VSB is usually derived (on
the motherboard) from 5VSB using a voltage regulator (on the Intel
Chipset Reference Board, 3.3VSB is derived from 5V_DUAL).
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.
System Design Considerations
Dual-Processor") to satisfy the S3 ACPI power
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820 Chipset Reference Board.
6
or Appendix B,
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820
6-1