Technical The BIOS and CMOS Power Management

Power Management Set-up

The following describe the fields and each option, found on Power Management Set-up page of popular motherboards.

Power management is the master control for the four power saving modes, doze, standby, suspend mode and HDD power down mode. This field allows you to select the type of power saving management mode. Usually there are four selections for power management. In order to use CPU overheat protection the power management option should be enabled. (Have not yet tested with ACPI).

Disabled: No power management support.
User Define: Users can define their own power management. Each of the ranges are from one minute to one hour. Except for HDD power down which ranges from one minute to fifteen minutes.
Min Saving: Predefined timer values are used such that all timers are in their MAX. values, one hour, one hour, one hour and fifteen minutes respectively.
Max. Saving: Predefined timer values are used such that all timers are in their MIN value, one minute.

PM Control by APM

A software interface between hardware-specific power management software and an operating system power management driver. The BIOS sends a message to the operating system to suspend.

This field allows you to use the advanced power management device to enhance the Max. power saving mode and stop the CPU's internal clock.

No: System BIOS will ignore APM when power managing the system.
Yes: System BIOS will wait for APM's prompt before it enter any PM mode e.g. DOZE, STANDBY, SUSPEND or HDD power down.

Note: If APM is installed & there is a task running,  the APM will not prompt the BIOS to put the system into any power saving mode. If APM is not installed, this option will be set to no.

Video Off option

This specifies the power saving state that the VGA video subsystem enters after the specified period of display inactivity has expired.

Always on: System BIOS will never turn off the screen, the video is always on.
Suspend: The video is set off when the system enters SUSPEND mode.
Older boards may include other options:
Susp, Stby => Off: Screen off when system is in STANDBY or SUSPEND mode.
All modes => Off: Screen off when system is in DOZE, STANDBY or SUSPEND mode.

Video Off Method

This field defines the video off features. The method of video power saving. There are three options.

Blank Screen: The BIOS will only black the screen when the system gets into power management mode and writes blanks to the video buffer.
V/H SYNC + Blank: Writes blanks to the video buffer, and turns off the vertical and horizontal scanning.
DPMS: Allows the BIOS to control the video display card if it supports the DPMS feature.

Modem Use IRQ

Defines the interrupt request (IRQ) being used by the modem (if any) on your system. Activity of the selected IRQ always awakens the system.

Suspend Switch

This setting is used for enabling or disabling the hardware suspend switch on some motherboards.

Enable: If the user presses this button then the system will enter into suspend mode. All devices except the CPU will be shut off. The CPU enters SMM mode.
Disable: No function even if the user presses the button.

Power Button / Soft-Off by PWRBTN

This field defines the power off mode when using an ATX power supply.

Instant Off: Allows power off immediately upon pressing the power button.
Delay 4 sec: the system powers off when the power button is pressed for more than four seconds or enters the suspend mode when pressed for less than four seconds.

HDD Off after / HDD Power down

When enable and after the set time of system inactivity, the hard disk drive will be powered down while all other devices remain active.

Disabled: Disable HDD power down mode function.
1Min ~ 15Min: Enable HDD power down mode between one and fifteen minutes. The motor on the HDD is turned off after the specified period of hard drive inactivity has expired.

Doze Mode

This field specifies the length of time of system inactivity while in full power on state before the computer enters doze mode and motivates the enable 'Wake Up Events In Doze Standby' / 'PM Events'.

Disabled: The system will never enter Doze mode.
1Min-1Hr: Defines the continuous idle time before the system enters Doze mode. If any item defined in 'Wake Up Events In Doze & Standby' / 'PM Events' is ON and activated, the system will return to full power.

After the selected period of system inactivity, the CPU clock runs at a slower speed while all other devices still operate at full speed. Some older motherboards may only put the system performance down to twenty percent.

Fan Off Option

This field sets the value used to enter the fan in Suspend mode.

Suspend: Set the system fans off if the system enters Suspend mode.
Always On: Set fan always on.

Standby Mode

This field specifies the length of time of system inactivity while in full power on state before the computer enters standby mode and motivates the enable 'Wake Up Events In Doze & Standby' / 'PM Events'. This field may not appear on modern motherboards.

Disabled: The system will never enter Standby mode.
1Min ~ 1Hr: Defines the continuous idle time before the system enters Standby mode. If any item defined in 'Wake Up Events In Doze & Standby' / 'PM Events' is ON and activated, the system will return to full power.

After the selected period of system inactivity, the fixed disk drive and the video shut off while all other devices still operate at full speed.

Suspend Mode

This field specifies the length of time of system inactivity while in full power on state before the computer enters suspend mode and motivates the enable 'Wake Up Events In Doze & Standby' / 'PM Events'.

Disabled: The system will never enter Suspend mode.
1Min ~ 1Hr: Defines the continuous idle time before the system enters Suspend mode. If any item defined in "Wake Up Events In Suspend" / "PM Events" is ON and activated, the system will return to full power.

After the selected period of system inactivity, all devices except the CPU will be shut off. Suspend Mode preserves data and parameters. Processing will not be performed until

Wake up events in Doze, Standby and Suspend Mode / PM Events

These options enable event monitoring on the specified hardware interrupt request lines (IRQ). Events which can prevent the system from entering a power saving mode or awaken the system from such a mode.

ACPI Function

Advanced Configuration And Power Interface is a system interface that provides a standard way to control power management and Plug and Play functions of the computer hardware. ACPI allows the computer motherboard to describe its device configuration and power control hardware interface to the operating system. This allows the operating system to automatically turn on and off standard devices, such as CD-ROM's, network cards, hard disk drives, and printers connected to the computer. The BIOS performs the necessary initialization process and hand over during boot and when returning to full power mode.
Power Management through ACPI allows the operating system (Microsoft has OnNow) to control power in the system. For ACPI to fully function the device drivers and applications used by the operating system must be ACPI aware. Certain applications or device drivers may crash the system or fail to let the system resume to full power mode.

Modem Ring Resume

If this field is available on the motherboard, the option enables the modem ring to wake up the computer system from a power saving mode.

RTC Alarm Resume

This field enables the user to set the option to enable an RTC Alarm (real time clock) to wake up the computer system from power saving mode. When this option is enabled another field allowing the user to set the alarm time on, appears. The additional field has options for date, hour, minute and second.

VGA / LPT & COM / HDD & FDD / DMA/Master

When any of these options are enabled or set to on, they enable event monitoring on the specified hardware IRQ when the computer is in power saving mode. The computer enters the full power on state if any activity occurs.

Primary INTR

Setting this option to on sets the system to wake up from suspend mode if activity is detected from any enabled IRQ channels. Setting this option to off will neither prevent the system from entering power saving mode or cause the system to fully power up.

Throttle Duty Cycle

Uncertain at this stage but it may have something to do with the percentage of power the CPU reduces to when the highest temperature set is reached.

CPU Temperature

This field sets the highest temperature that will slow the speed of the CPU down. At this stage I think the speed is set by the Throttle Duty Cycle field.

Chipset Set-up

Plug And Play Set-up