\[ Excerpted from LBL-39466, "User Guide to Power Management in PCs and
Monitors", pages 23-26 \]

**4.4 Trouble Shooting**

In the past, the only solution to many power management related problems
was to disable power management entirely. This is no longer the case.
Power management is now more flexible and has more options, which allows
specific problems to be addressed without disabling all power management
features.

  --------------- ------------------ -----------------------------------------
  **Table 4.2:                       
  Recommended                        
  Delay times for                    
  Power                              
  Management**                       

  **Item**        **Delay time**     **Comments**

  **Hard disk**   10 to 20 minutes   depending on how quickly it spins back up

  **Processor**                      

  Doze            20 seconds to 1    if applicable
                  minute             

  Standby          5 minutes         

  Suspend         10 minutes         

  Hibernate        2 hours           due to longer recovery time

  **Monitor**                        

  Dim              5 to 10 minutes   if applicable

  Standby          5 to 15 minutes   depending on recovery time and if 'dim'
                                     mode operating

  Suspend         15 minutes         

                                     
  --------------- ------------------ -----------------------------------------

When making trouble shooting decisions, it is important to weigh the
potential energy savings against the costs of a particular power
management option (in terms of recovery time and system interference).
Both savings and costs depend on how the computer is used, but a few
general guidelines should be kept in mind. Power management of monitors
typically saves more energy than it does for PCs (unless the monitor is
turned off nights and weekends but the PC is left on). Monitor power
management is less likely to be defeated by network activity, and is
also less likely to cause problems than PC power management. Even if
there is some reason why the PC can't accomplish power management, or
power management interferes with use of the PC and has to be disabled,
the monitor can usually still be power-managed. People who are
particularly fond of their screen art should try to configure the system
to display the screensaver for a few minutes, then begin the power
management cycle (some screensavers can do this; in other cases the
screensaver and BIOS can work together).

**Common Problems**

*I can't tell if the PC is powering down*

Many PC power management functions have no discernible delay in
returning to full power, so that it can be difficult to determine if
power management is working. To be certain that power management is
occurring, it is necessary to actually measure the power the system uses
(see Appendix D), which is not a realistic option in most offices. Apart
from that, the most obvious feedback of a PC powering down is hearing
the hard disk power down and spin back up. Recovery from 'doze' modes is
nearly instantaneous, and even lower-power modes have very quick
recovery times, making it difficult to be sure that PC power management
is occurring.

*I can't tell if the monitor is powering down*

If the recovery from a blank screen is instantaneous, then the monitor
is probably not in a suspend mode (the lowest power state), though it
could be in the first power management mode, sleep. Some monitors will
"beep" as they revive, and others signal low-power modes with an
indicator light on the front of the monitor. Check the manual to see if
any such indication happens automatically (or is optional) during
low-power modes.

*Power management is enabled, but not working*

There are many reasons this could be occurring, including:

• The 'main switch' for power management is on, but subsidiary switches
(e.g., for each low-power mode) are off. Turn these on and see if power
management occurs (see Figure 4.1; the switches are generally found in
BIOS setup screens).

• The timers are set to such long delays that the power management does
work but rarely has the opportunity. Try reducing the delay times.

• The network (or network operating system) is keeping the PC awake. To
diagnose the problem, try rebooting the machine with the network cable
disconnected, or even with the network card removed to see if this
changes power management behavior; also check the network operating
system documentation. A different network card may not have this
problem, but the replacement cost may be greater than power management
savings warrant.

• The operating system may not support power management.

• The PC may have been upgraded in a way that interferes with power
management. If it was custom built, rather than a standard model from a
manufacturer, parts may not properly work together to accomplish power
management. There may be no solution to this problem.

• If the monitor is not entering sleep mode, it may not be capable of
power management, or a screensaver may be interfering with power
management operation. To help diagnose the problem, try temporarily
using a monitor that you know works well with power management, and
changing screensavers to the blank screen option.

• Application software is keeping the system awake. For example, some
software for controlling CD-ROM drives will poll the drive frequently to
see if a disk has been inserted; some printer software routinely polls
the printer for its status. Disabling an IRQ may alleviate this, but the
system may go to sleep while a CD is playing, or while a long print job
is in progress.

*Power management is occurring, but only partially or with extremely
long delays*

The machine may be configured to operate this way for a good reason,
such as to avoid network problems or avoid long recovery delays.
However, it is also possible that there is no good reason for the
settings. Try to determine why the machine was configured how it was,
and whether it can be set to more typical settings, such as those
recommended in this guide.

*The user tells me power management causes her problems*

In certain environments power management can cause problems, and it may
be necessary to leave power management disabled. However it is important
to address specific complaints (e.g., "The hard disk spins down every
five minutes and takes forever to spin back up") rather than general
ones ("Power management is causing problems"). It may be possible to fix
*specific* problems by changing power management settings. *General*
problems may not be the fault of power management at all. Power
management is often a convenient scapegoat for system problems,
sometimes resulting in power management being unnecessarily disabled.

It is important to keep in mind that users who have had trouble with
power management in the past (or have heard stories from others who have
had problems) are often distrustful of the technology, even though great
improvements have been made. Educating users about power management will
make them more comfortable with the technology.

*The monitor goes to sleep, then wakes up a few minutes later.*

This can be caused by some screensavers. If that is the case, the
screensaver can usually be reconfigured to not do this. Avoid
screensavers or screensaver options that require hard disk access, and
make sure that the screensaver delay time is less than the first monitor
power management delay time. Some networks can cause a machine to
reawaken after a short period of power management. See if the machine
power manages correctly when not connected to the network, and if so, if
the server or network card can be reconfigured.

*A calculation which used to take 2 hours now takes all night to finish*

This occurs if the PC goes into the doze mode, slowing the processor
clock, while the computation is in process. If such calculations are
rare, then either doze or power management in general can be disabled
while it is in process. If the computer is routinely used in this way,
disable doze only so that the rest of power management will occur.

*I can't find the power management controls in the BIOS*

That machine might not be capable of power management. PCs that appear
similar on the outside can be quite different on the inside, so that
even if one PC in the office has power management, a similar PC might
not. Try calling the manufacturer and provide them with the serial
number to help determine if the machine has power management features.

*The user has locked the BIOS with a password*

Consider changing the power management settings with the user present so
that she can be reassured that the changes are acceptable.

*The PC (or monitor) won't return to full-on status with keyboard or
mouse input*

Check the BIOS settings. The interrupt requests for the keyboard or
mouse may not be enabled (these are typically IRQ1 and IRQ12
respectively).

*The PC loses its network connection in low power modes or fails to
respond to network activity*

Power management may be slowing CPU activity too much for it to respond
to network activity. Some versions of BIOS have options to specify how
much to reduce the processor speed in doze or standby. Try reducing the
speed reduction value; this speeds up the processor (when in the
low-power mode) and increases its ability to respond to network
activity. If the problems persist, or if changing the speed is not an
option, try disabling the doze or standby option.

*My screensaver is password protected. Every time I want to reactivate
the monitor, the hard disk has to spin back up.*

If password protection cannot be disabled for security reasons, try
increasing the delay time for hard disk spin down (to 15 minutes or
more) in order to reduce the occurrence of the problem. If this is still
unacceptable to the user, it may be necessary to disable the hard disk
spin-down. The energy savings potential for the monitor are greater than
from the hard disk, so keeping power management enabled for the monitor
should be the priority.

*Power Management works in Windows, but not in MS-DOS.*

DOS can override the BIOS. Try routinely turning the machine off *or*
remaining in Windows.

*My computer must be on all night because the disk is backed up over the
network in the middle of the night*

One response to this situation is to move the back-up time to during the
work day. Another is simply turn off the computer when not many files
have been changed that day. A third response (on machines capable of it)
is to have the system completely power down at a time at which the
backup will have finished.

*My computer takes too long to recover from power management*

Consider increasing the delay times for the power management modes that
are causing the problem. The hard disk recovery time is often a source
of user complaints about excessive recovery time. If an auto-save
feature is spinning up the hard disk while the person is typing,
consider turning off that feature. Try increasing the delay time for the
hard disk while keeping them as-is for the processor and monitor. Even
if some power management methods must be disabled for the user, don't
turn off all features---keep active the power management features that
are not interfering with work.

*My computer shuts off entirely when power management is enabled.
Rebooting the system is time consuming, and I have lost data when the
system has shut down.*

A few models of PCs (most notably early Apple PowerMacs) shut off
entirely rather than go to sleep. Few users find this acceptable, so be
cautious about enabling this form of power management.