BIOS Settings - Power Management



This section contains the various settings that you can use to 
control your system's automatic power management settings. The 
pros and cons of using it are in this section on system care .

	Note: In many ways, automatic power management is still 
"not ready for prime time", at least in my experience. Enabling 
power management can cause problems in your system because many 
software programs aren't prepared to properly deal with having 
the processor power down or the hard disks turn off, etc. You 
can certainly use power management, but be prepared to disable 
some of the settings if you have problems with them. I strongly 
recommend disabling all power management features when initially 
assembling a new system or performing upgrades or new software 
installations. If you do not, you will have a hard time figuring 
out what is causing any problems you might experience.


Global Power Management Setting

This is a setting that, if present, globally enables or disables 
power management. When set to "Disabled", the other settings in 
this section will typically be either locked out (so they cannot 
be changed) or else they will simply be ignored.


Video Power Down Mode

If present, this setting controls the method used to put the 
monitor into low-power mode. The typical options for this 
setting are: 

	DPMS: Select this option if your monitor supports the 
	DPMS standard for monitor power management . This is 
	the preferred and usual default setting; most modern 
	monitors do support DPMS. 

	V/H Sync+Blank: Selecting this option causes the video 
	card to shut down the vertical and horizontal sync 
	signals to the monitor, as well as sending blank data 
	to the monitor. 

	Blank Screen: This option causes the monitor to be 
	blanked only. 


Video Power Down Timeout

This setting controls how long the system must be idle for the 
video to be powered down. It is specified in minutes, or set to 
"Disabled". How long you set this for depends on your personal 
taste and how you use your system. Note that a colorful "screen 
saver" really doesn't save any power at all over regular use of 
the monitor--the monitor is still on and displaying information 
either way.


Hard Disk Power Down Timeout

This setting controls how long a hard disk must be left idle 
before it spins down. The default is "Disabled". In a system with 
more than one hard disk, an idle timer is normally maintained 
individually for each. The choice of setting here depends a lot 
on how you use your system, as well as your personal opinion on 
the question of whether or not hard disks are better off running 
continuously or spinning down when not in use. See here for a 
discussion on this issue .


Doze Mode Timeout

This setting defines the number of minutes before the system 
enters "doze mode", the first level of system inactivity 
shutdown. The exact definition depends on the system, but in 
general this mode means that the processor slows down to a 
minimal activity level while other parts of the system keep 
running as normal. The default for this setting is 
usually "Disabled".


Standby Mode Timeout

This setting defines the number of minutes before the system 
enters "standby mode", the intermediate level of system 
inactivity shutdown. The exact definition depends on the system, 
but in general this mode means that the processor slows down to 
an even lower activity level than doze mode, and the video and 
hard disk drives are powered down. The default option is 
"Disabled".


Suspend Mode Timeout

This setting defines the number of minutes before the system 
enters "suspend mode", the deepest level of system inactivity 
shutdown. The exact definition depends on the system, but in 
general this mode means that all system devices are shutdown 
(except for any that the BIOS is specifically told to keep 
running) and the processor is shut down to a trickle mode. The 
default option is "Disabled".


IRQ Wake-Up Events and Activity Monitors

When the system enters a power-down mode, it will look for 
activity to tell it when to wake back up. Normally you wake the 
system back up either by pressing a key or moving the mouse. 
However, you may want the system to wake up in response to other 
events. For example, you might want the system to wake up when 
activity on the modem is detected, if your PC answers incoming 
faxes. Some BIOSes give you the ability to specify whether or not 
activity on an IRQ will wake up the system.

The BIOS monitors the system for "activity" to determine when to 
enable power management. You can tell the system what it should 
consider activity and what it should not, in other words, what 
sorts of events on the PC hould reset the idle counter for power 
management. For example, in almost every case a movement of the 
mouse or a keypress could be considered activity. However, if 
you have a sensitive mouse that can move slightly in response to 
vibration, you might want to set the BIOS so that movement on 
the mouse will not reset the power management countdown timers.

There will normally be a separate setting for each IRQ. For each 
one, the options will typically be: 

	Wake Up: Activity on this IRQ will wake up the system 
	when in a power-down mode. 

	Monitor: Activity on this IRQ will reset the system idle 
	countdown timers. 

	Both: Activity on this IRQ will both wake up the system 
	when powered down and reset the idle timers when 
	powered up. 

	Neither: Activity on this IRQ will neither wake the 
	system nor reset idle timers. 

The default for these depends on the system. Some BIOSes use 
similar controls with different names, or may separate the wake 
up event controls from the monitoring controls. If you are using 
power management you will want to tailor these based on what 
interrupts (devices) are in use on your system. Look here for 
information on what the typical IRQ allocations are on a PC .

	Tip: For a system with a PS/2 style mouse, the mouse will 
be on IRQ 12. For a system with a serial mouse, the mouse will be 
on whatever IRQ is assigned to the COM port the modem is using. 
This is usually COM1, which uses IRQ 4.

	Note: IRQ1, which is generated by the keyboard, is not 
usually listed here as it always causes a wake-up from power 
management, and cannot normally be disabled.
