new power
on hp pcs
Why is Power Management
a PC that is available 24 hours a day, with highly
reduced wakeup times, yet still save energy by using
low power sleep modes.
Power management is essential because it:
The specific advantages of ACPI over APM include:
• Helps cut power costs by reducing the amount of
energy used by PCs
New Hibernate mode
This is a very low power consumption mode that
also allows the PC to be quickly available. In
Hibernate mode the PC appears to be switched off
(power off). The PC system context is saved to hard
disk and then reloaded (after the BIOS is initiated)
for a fast wakeup. This is implemented in Windows
2000 and can be used in any recent or new HP PC.
Resistance to power failure
The Hibernate mode is resistant to power failure as
the OS state is saved to hard disk, so power out
during Hibernation will not cause memory loss. The
OS and current program states are saved until
power is restored when the PC can automatically
reload the last state and continue operation.
Suspend to RAM
This is similar to the Hibernate mode described
above, only there is less power saving and wakeup
is faster, since the system context is saved in main
memory. This is available on selected HP PCs.
Highly configurable
Since control is centered in the operating system,
you can configure ACPI power management
parameters more easily. (APM is centered in the
BIOS and requires you to restart the PC to configure
power management.) ACPI also provides more
features, with a wider range of configuration
parameters, offering higher flexibility and greater
user control. This is advantageous to both users and
systems administrators (for desktop management
A configurable power switch
This feature allows system administrators to choose
what the PC does when the user presses the power
switch. You can select very low power sleep states
(Hibernate) or ultra-fast wakeup (Standby) for
increased availability. This is discussed in
“The Power Button and Unexpected Wakeup” on
page 6.
More open to evolution
The ACPI standard not only allows the operating
system and hardware to perform coordinated power
management, it also allows power management
technology to evolve independently in the operating
system and in the PC hardware.
• Allows the PC to meet and even exceed energy
consumption regulations worldwide.
Advance Power Management (APM) was the first
major open industry standard developed to meet
power management needs in personal computers.
APM is controlled from the PC’s BIOS. The BIOS
establishes a connection with an operating system
driver and in this way provides power management
instructions to the operating system.
APM was provided on all HP PCs, and has been
successful in reducing the energy consumption of
millions of PCs worldwide. However, the computing
world has changed radically in the few years since
APM was developed. Recent leaps in technology and
new uses for PCs have rendered APM ill-equipped to
deal with power management tasks.
These emerging APM drawbacks include:
• Difficulty in meeting the increasingly strict power
saving regulations
• Diminished availability. Computers are increasingly
being used for demanding tasks requiring 24-hour
availability. A PC that goes into an APM low power
mode is unavailable for use and remains so until it
has gone through the lengthy wakeup or startup
Typically, there has been a strict trade-off between PC
availability and the energy saving achieved.
The latest technology is ACPI (Advanced Configuration
and Power Interface). This is an open industry standard
created by, among others, Microsoft and Intel. It
addresses the drawbacks in APM and incorporates
many improvements.
Unlike APM, ACPI is controlled by the operating
system. This allows easier control and configuration of
power management (since the operating system is
more accessible).
ACPI also drastically reduces the trade-off between
energy saving and PC availability. Now you can have
• More robust and reliable
ACPI allows improved coordination between the
operating system and the PC hardware, as well as
centralized control by the operating system, making
it more robust and reliable.
These advantages are only available if you are using
an ACPI-based operating system, such as Windows
98 Second Edition or Windows 2000.
ACPI Power
System Name
How Does ACPI Work?
Hibernate Mode
The Hibernate feature is an example of how ACPI
power management is implemented in Windows
The PC can be configured to go into Hibernate mode
when the user presses the power button, or after a
preset delay when the PC is not being used.
This table shows the ACPI power management states. You can use this as a guideline when configuring power
management to achieve power saving goals.
The PC is in this state during normal use. All
devices in the PC are usually powered on.
The lightest sleep state. The PC hardware
maintains its context. Usually, only the monitor
and disks are powered off. The operating system
goes on Standby.
Similar to S1 except CPU and cache are also
powered off. This state is not currently used.
Wakeup by
In ACPI, called ‘Suspend to RAM’. System
context is saved to main memory and is then
used for a fast wakeup. This Standby mode S3 is
used instead of mode S1 on PCs that support it.
All devices in the PC are powered off. PC context
is saved to hard disk and is then used for a fast
startup. The operating system shuts down.
During wakeup from mode S4, the BIOS reinitializes and the operating system performs a
fast startup using the disk image.
In ACPI, called Soft Off. The operating system
shuts down. During wakeup from S5, the BIOS
re-initializes and the operating system performs a
complete reboot.
See “The Power Button and Unexpected
Wakeup” on page 6.
Time Required by the PC to
Become Available
PC Power Use
Not Used
[see note*]
* Remote Power On from S5 State: Current Operating Systems (up to Windows 2000, Service Pack 2) do not support RPO from
S5 . However, new HP BIOSs will support RPO from S5 mode. Check the HP websites dedicated to your PC model (see page 6)
for news and BIOS updates.
n System context
main memory must be maintained to preserve the
system context. However, since main memory is faster
than the hard disk, wakeup takes less time from
“Suspend to RAM” mode.
o All PC devices
powered down
The same events that trigger the PC to wake up from
Hibernate mode also work for Suspend mode.
Additionally, pressing any key on the PS/2 keyboard
can also wake the PC up from Suspend to RAM mode
(this keyboard wakeup can be disabled in the OS
power management options).
This illustration shows how the Hibernate mode works.
saved to
hard disk
Under Windows 2000, ensure the OS option
“Suspend to RAM” has been selected in
Start>Settings>Control Panel>Power Options
if you want to activate this mode.
The PC’s system context (contents of main memory,
position of all programs, etc.) is stored on hard disk
and then all devices are powered off. The PC goes
into state S4.
When the PC gets a wakeup command, it initiates the
BIOS then reloads the system context from the hard
disk. In this way the PC starts up very quickly from
where it left off, becoming quickly available for the task
at hand.
Wake Up from Hibernate
All PC devices
powered on
Which Operating Systems
Support ACPI?
ACPI Mode Supported
Windows NT 4
The events that trigger the PC to wake up from
Hibernate mode are:
• Pressing the PC’s power button (or the space bar on
PCs that support this feature)
• A scheduled event
(such as a late-night backup)
• A wakeup command from the network
(typically, for desktop management tasks such as an
automatic software upgrade)
• An incoming call on a modem.
Suspend to RAM Mode
The new “Suspend to RAM” mode (S3) works in a
similar fashion, except that the system context is saved
to main memory. This state uses more power since the
No integrated power management
Windows 95
APM only
Windows 98 Gold
APM recommended
Windows 98 SE
Windows 2000
System context
recovered from
hard disk
APM only
Windows 2000
Windows 2000 is currently the operating system that
has the most complete ACPI power management
From the Windows Start menu, the user has the option
to Shut Down (S5) or go into Hibernate mode (S4) if
this is enabled in Power Management, or go into
Standby (S3 or “Suspend to RAM”).
Windows 2000 power management options are
configurable from the Power Options icon in
Start>Settings>Control Panel. Here you can set the
action of the PC’s power switch to instigate Standby
(S1 or S3), Hibernate (S4), or shut down the PC (S5).
You can also select the devices allowed to signal a
wake-up to the system. The wake-up is carried out
when an event is received from any of the devices you
have set as ‘active’ in the Power Management tab of
Device Manager (the Device Manager can be opened from
Start>Settings>Control Panel>System>Device Manager)..
To set a device input to wake-up the PC under
Windows 2000, from your desktop right-click on the
My computer icon. Select Properties >Hardware >
Device Manager. Click on the device to select it (for
instance Keyboard) then right-click on the highlighted
device and select Properties. Go to the Power
Management tab and toggle the option "Allow this
device to bring the computer out of
Implications and
Recommendations for the HP
PC User
Check that the BIOS Power Management options are
configured correctly to enable ACPI with OS control.
The available BIOS options depend on the version of
BIOS in your PC (see tables on page 6). It is
worthwhile to view the BIOS Setup to confirm which
options are available and active, particularly if you
have upgraded to Windows 2000 from an earlier
Standby Modes S1, S2, S3
Windows 98
Windows 98 Second Edition also implements ACPI
power management, although the features are not as
rich as Windows 2000. In particular, there is no
Hibernate mode in Windows 98.
Windows 98 First Release also supports ACPI power
management. However, most of the HP PCs shipped
with Windows 98 First Release have an APM BIOS by
default. If you use Windows 98 First Release on these
systems, HP recommends that you use APM power
From the user’s point of view, many of the features
provided by APM and ACPI are similar but they do not
always work in the same way.
Operating Systems may refer to the modes S1, S2 and
S3 as ‘Standby’ without always making clear the
differences between these three modes.
When the user selects a Standby option in the OS, the
software will decide which of these modes is
compatible with the software/hardware environment
and also checks the wake-up capabilities of the
hardware present, as some hardware can only be
woken from mode S1. The sleep-mode compatible with
these parameters and also providing the greatest
power saving (deepest sleep) is selected.
This selection is necessary as some hardware cards do
not support S3, which is a relatively new standard.
When not sure if a PC is in mode S1 or Suspend to
RAM mode S3, test by opening the CD tray using the
pushbutton control. If the tray opens, this indicates that
the PC is in mode S1.
Windows 95
Windows 95 supports APM but not ACPI. If you use
Windows 95, APM power management is
Windows NT 4
hp moves forward with acpi
Windows NT 4 does not include any built-in support
for power management. However, HP provides Soft
PowerDown, a Windows NT utility offering a useful
power management feature.
HP is fully committed to ACPI and its advantages.
All new HP PCs support most ACPI features and
ship with Windows 98 Second Edition or
Windows 2000, Microsoft’s latest operating
systems which support ACPI.
For More MS Windows Information
In fact, HP has been committed to ACPI for some
time. Most HP PCs shipped in the last few years
have both APM and ACPI implemented in the
BIOS, allowing you to choose the power
management scheme to best fit your needs. So
you can even benefit from many of the
advantages of ACPI when you update to
Windows 98 SE or Windows 2000.
For more information about Windows operating
systems, refer to Microsoft’s web sites:
APM is supported. Recent Linux kernels support ACPI.
LINUX v2.4 with ACPI will be available early in 2001.
For full information see LINUX documentation for your
version and/or FAQs on line (many sites).
To learn if your HP PC supports Windows
2000, consult the white paper “HP
Windows 2000”, available at
Power States available to HP PC models
The PC Supports these States
for APM and/or ACPI
S4 (Hibernate)
S5 (Shut Down)
HP Vectra VLi8
ACPI check BIOS version
HP Vectra VL400
ACPI check BIOS version
HP Vectra VL600
Does Not Support S3
ACPI check BIOS version
HP Vectra VL800
ACPI check BIOS version
HP Kayak XU800
Does Not Support S3
ACPI check BIOS version
HP Kayak XM600
for ACPI check BIOS version
HP e-pc c10
HP e-pc s10
HP e-vectra
for ACPI check BIOS version
HP Brio BA410
RPO for APM only
* To support RPO from S5 the BIOS version and Driver version must both support RPO in S5 mode. See table below.
Remote Power On from S5 Mode
OS supporting RPO*
HP PC Model
3com LAN
1st BIOS version
to support RPO
1st 3com LAN driver
to support RPO
1st HP LAN driver
to support RPO
HP Vectra VLi8
ED 5.20
HP Vectra VL400
ED 5.20**
HP Vectra VL600
ED 5.20
HP Vectra VL800
[release early 2001]
ED 5.20
HP Kayak XM600
ED 5.20
ACC 1035
HP e-pc c10
HP e-pc s10
HP e-vectra
ED 5.20
The HP BIOS versions listed here are current or soon to be released. Check the HP website for your model of HP PC to find details.
* In all cases RPO is supported from the Shutdown mode (not from First Boot or Failure states)
**Also identified as “3C520HP” or by the 3COM version No.1.80.0000
The Power Button and Unexpected
The operating systems Windows 2000 and Windows
98 SE both enable software-configuration of the PC’s
power-on button. Depending on the chosen
configuration, the push-switch may not behave like a
hard-wired on/off switch, and the user should no longer
expect it simply to turn off the PC’s power supply. The
PC could instead go into a power saving mode such as
Hibernate, where it is still under tension.
Furthermore the PC can automatically power on, for
example for scheduled maintenance or remote
management. Users should realize that the PC can “turn
itself on” and that this is normal behavior.
PCs with a network card supporting RWU (Remote
Wake Up) can be woken up by the network in this way.
Most non-ACPI PC models equipped with a network
card that supports Remote Wake Up or RPO (Remote
Power On) can also be woken up or restarted by the
It may be difficult to discover if the PC is in a low power
state or is turned off (electrically isolated from the power
Considering these points, before any maintenance
action you should wake the PC and carry out a shut
down (S5) to ensure it is correctly powered off. Always
remove the PC power cable from the socket before any
maintenance actions. This ensures that the PC is ‘off’ and
disconnected from the power source. Please read current
HP documentation on “Servicing the PC” before starting
an intervention.
For the reasons described in “Desktop Management”, it
is recommended that you configure the power button to
Hibernate when running Windows 2000, or to
Standby if it is available on your PC model, running
either Windows 2000 or Windows 98 SE. This
ensures that you can perform remote management. In
addition these options provide a more rapid restart
than the system cold boot.
Your PCs can safely remain in one of these two states
when not in use, and need to be turned off only when
maintenance or physical relocation of the PC is
Using the Mouse
The mouse cannot be used to wake up the PC from
Standby or Hibernate. To wake up the PC from
Standby, the user can press any key on the keyboard
(from S1 only, on some HP PC models), the keyboard
space bar (on some HP PC models), or the PC power
The mouse is considered too unstable to be an effective
wake-up agent, as it is subject to accidental movement
or may even pick up vibration from the environment,
causing unwanted wake up.
To wake up from Hibernate mode, the user must press
the PC power button or the space bar on models that
support this feature.
On some older non-ACPI HP PCs, the mouse could be
used to wake the PC from a custom sleep state similar
to Standby. This sleep state is no longer used since
power management states are now standardized.
under Windows 2000 and ACPI. These BIOS versions
will be announced as they become available in 2000
and early 2001.
If you are planning to use remote desktop management
on ACPI-based PCs, with current HP BIOS versions you
should not make use of the off state (S5). Instead,
Hibernate is recommended, since you can then wake
up the PCs remotely using RWU (remote wake up). To
ensure that Soft Off is not used, you must reconfigure
the power button.
Also, it is possible to remove the option
from the Windows Start>ShutDown menu. To learn
how to do this, refer to Microsoft’s hardware white
paper “Windows Power Management Configuration
Tools Design Notes and Reference”, available at
Enable RPO
To enable Remote Power On, several settings may be
In the driver (e.g. under Windows 98).
Power settings are accessed in Start>Settings>
Control Panel >Power
In the BIOS (options vary depending on the BIOS).
At boot, press F2 to open the BIOS settings and
select Power Management.
For networked PCs the BIOS settings may also be
altered remotely using HP Toptools. See the HP Toptools
documentation or website for more information.
HP Utilities
For System Administrators
Recommended Operating Systems
To make use of the ACPI features provided by new HP
PCs, you need Windows 98 SE or Windows 2000. In
fact, on new HP PCs, one of these operating systems
will be provided preloaded on the hard disk or on the
CD that comes with the PC.
For the fullest set of ACPI features with HP PCs,
Windows 2000 is recommended. For example,
Hibernate mode is only available on new HP PCs
when using Windows 2000.
For manageability, Windows 2000 is recommended
rather than Windows 98 SE.
Desktop Management
New and recent HP PCs running Windows NT or
Windows 95 can be powered on from the off state
using RPO (Remote Power On).
However, for HP PCs running Windows 98 SE, or
running Windows 2000 with ACPI, you require the
new HP BIOS versions which support RPO from S5
HP Utilities that provided power management features
in non-ACPI based systems are to be phased out and
are not available for Windows 98 SE or Windows
2000. The features provided by these utilities are now
provided by Microsoft’s ACPI-based operating systems.
Non-ACPI Systems
ACPI Systems
HP Utility
Win 95
Win NT4
HP Safe Off
HP NT Lock
HP Soft PowerDown
Win 98 SE
Win 2000
Feature provided by
operating system
Servicing the PC
Before upgrading or servicing the PC, it is very
important to ensure that the PC is off (in S5 mode) and
not in Hibernation mode (S4).
If the PC is in Standby mode, there will be a flashing or
yellow indicator light on the PC’s front panel.
There is no way of telling if the PC is in Hibernate mode.
The best way to ensure that the PC is not in Hibernate
mode is to restart the PC then shut it down. To do this,
select Shut Down from the Start menu then under the
headingWhat do you want the computer to
do?select the option ‘Shut Downfrom the dropdown list.
If the Shut Down Option Has Been
RPO ‘out of the box’
New HP PC are delivered preloaded and ready to
function ‘out of the box’ as soon as they are powered up.
However, the Remote Power On (RPO) function requires
a continued power supply to operate correctly. When
your HP PC comes ‘out of the box’ it is in a state
equivalent to a power interruption.
If the ‘ShutDown’ has been removed from the list of
options, the following procedure is recommended to
ensure the PC is not serviced while in S4 mode.
To set up RPO, you should connect up all peripherals
and switch on the PC. Enable the Hibernate option then
put the PC into Hibernation mode by selecting
Start>Shutdown>Hibernation. The computer is now
able to respond to any RPO request.
From the box:
1 Restart the PC by selecting Start>Shut Down and then
choosing ‘Restart’ from the drop-down menu.
Connect all PC peripherals and power cable
2 When the PC has fully shut down and is just beginning
to restart (you will see the initial Brio, Vectra, Kayak or
HP logo), press the power switch to shut down the PC.
Press the Power Switch to power-up the PC
After the OS is running, enable Hibernate in
Start>Settings>Control Panel>Power Options.
Put the computer into the Hibernate mode by selecting
Start>Shut Down>Hibernate.
3 Remove the power cable to isolate the PC.
Alternatively, you can log on to the PC as Administrator
and then activate the Shut Down option in
Start>Settings>Control Panel>Power Options.. The choice
‘Shut Down’ will then be available in the dropdown
menu headed ‘What do you want the computer
to do?’. Use this to choice to shut down the computer
and then remove the power cable.
Once servicing or upgrading has been completed, the PC
will perform the full startup procedure, taking into account
any changes to the PCs configuration.
Note that if the PC is serviced (power off) while in the
Hibernate mode, the power up sequence may easily
cause an OS crash with unpredictable and undesirable
This is particularly the case when the hardware
configuration has been altered in the serviced PC.
Hibernate will assume there has been no power
interruption and will attempt to reload the previous OS
state from the hard disk without verifying the state of any
hardware present (which may require initialization after a
power out).
The full boot from S5 checks all hardware and carries out
all initialization required.
Alternatively, If your PC fully supports RPO from S5 and
you have enabled the option in the BIOS, you can put
the PC into Hibernate mode simply by pressing the
Power Switch a second time.
The PC is now in Hibernate mode and ‘set’ for RPO.
Note: it is possible that at the next use of the PC
following this initialization a glitch will be noticed (once
only) when the PC restarts. This is normal, and is dealt
with by the PC during the course of the restart. Your HP
PC is now operative.
For More Information
If the PC looses power in Hibernate (S4) or soft off (S5)
mode however, there will be no data loss. In fact, it is as
if the PC was already powered off.
The ACPI Specification
Microsoft’s web site on power management, ACPI,
APM, and Windows operating systems
Power Loss in the Different Power
Management States
If the PC looses power in S1 or S3 Standby mode
(through a power failure in the building or by pulling out
the PC’s power cord), you will loose any unsaved data. In
this case it is just as if the PC lost power while it was on.
The ACPI web site
Microsoft’s hardware white paper “Windows Power
Management Configuration Tools Design Notes and
Reference” is available at
Intel’s web site on ‘Instantly Available’ and ACPI
HP’s white paper “HP Windows 2000” discusses the
support offered for Windows 2000 (including its
power management features) on HP Desktop PCs.
It is available at