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6-4

System Power

Table 6-2 describes system activity for each system power state and describes events that cause the
system to enter each state. System power states are listed here in decreasing order from higher to lower
power usage. The system can be configured to use some, all, or a combination of these system power
states. These states are described in more detail later in this chapter, see “Power Management States and
BIOS Configuration Options” on page 6-5. Also note that timeouts, such as the suspend timeout and hard
disk drive spin-down timeout can be configured separately in the BIOS or controlled by system or
application software through APM or ACPI.

Table 6-2 System Power States

* The system can be configured to use Suspend-to-RAM mode or Suspend-to-Disk mode. See “Power Savings

Menu Options” on page 3-13 for more information. If Suspend-to-Disk is used, the system must have a
suspend-to-disk partition or file, see “PHDISK Hard Disk Preparation Utility” on page 3-29 for more information.

System State

System Activity

Events Causing System to Enter State

Fully On Mode

System is running. CPU, system bus, and all
other active interfaces operate at full speed.

From Standby or Idle mode: user activity
detected.
From Off mode: system started.
From Suspend-to-RAM mode: system
operation resumed (Suspend/Resume button
pressed, resume on modem ring, resume on
time).

Idle Mode

CPU speed reduced to the speed selected for
the Idle Mode CPU Speed BIOS option.

See “Idle Mode” on page 6-5 and “APM CPU
Idle Mode” on page 6-8 for more details on
Idle mode.

Idle mode timeout occurs. (No system activity
for 1/2 second.)

Note: The low battery warning condition (less
than 12% charge) will force the system to use
Idle mode. Low battery warning (audible beep)
is heard if Audio is enabled in the BIOS.

Standby Mode

CPU enters stop-grant state (CPU stopped).
Hard disk drive enters standby state (spun
down).
Display and backlight are turned off.

Standby timeout occurs.

Suspend-to-
RAM Mode*

Resume system logic remains powered
(Suspend/Resume button circuitry) and RAM
remains powered to maintain active data.
All other devices are powered off.

Suspend timeout occurs.

Suspend request (issued by software or
Suspend/Resume button pressed).

Critically low battery. Note that a critically low
battery forces system into Suspend-to-RAM
mode regardless of the Suspend Mode setting
in the BIOS.

Suspend-to-
Disk Mode*

Active system data is saved to the hard disk
drive. (Data is saved to a partition or file
depending on save to disk configuration.)
System is fully powered off except for logic
components required for Suspend/Resume
button operation.

Suspend timeout occurs.

Suspend request (issued by software or
Suspend/Resume button pressed).

Suspend-to-Disk mode can be entered either
by pressing the Suspend/Resume button (if so
configured in BIOS) or by pressing the
Suspend-to-Disk hotpad which will always do a
Suspend-to-Disk.

Off Mode

System is fully powered off except for logic
components required for Suspend/Resume
button and real-time clock operation.

System shutdown.
Suspend/Resume button pressed (if
configured as Power On/Off button in BIOS).