Intel AP440FX specifications Advanced Power Management APM, Advanced Power Control APC

AP440FX Motherboard Technical Product Specification

3.8 Advanced Power Management (APM)

This section describes the use of System Management Mode (SMM) by the BIOS. The BIOS supports APM version 1.2. APM is enabled in BIOS by default; however, the computer must be configured with an APM driver to utilize the system power saving features. Windows 95 enables APM automatically upon detecting the presence of the APM BIOS.

The energy saving Standby mode can be initiated by one of the following:

∙a keyboard hot-key sequence set by the user

∙a time-out period set by the user

∙a suspend/resume button tied to the front panel sleep connector.

When in Standby mode, the motherboard reduces power consumption by utilizing the Pentium Pro processor’s SMM capabilities and also spinning down hard drives and turning off VESA DPMS compliant monitors. The user may select which DPMS mode (Standby, Suspend, or Off) to send to the monitor in Setup. The ability to respond to external interrupts is fully maintained while in Standby mode allowing the system to service requests such as an in-coming fax or network message while unattended. Any keyboard or mouse activity brings the system out of the energy saving Standby mode. When this occurs the monitor and IDE drives are turned back on immediately.

Because SMM uses its own address space, the pointers to interrupt service routines in protected mode do not necessarily point to the executable interrupt service routines when the processor goes into SMM. Interrupts are disabled upon entry into SMM. Any program that wants to use interrupts during SMM must provide a valid interrupt service routine and place a pointer to it in an interrupt descriptor table before renabling interrupts.

Windows 95 places an Energy Star compliant monitor in video standby mode after a period of system inactivity. Windows 95 uses the motherboard BIOS to put the processor into SMM. The motherboard BIOS in turn invokes the video BIOS to place the monitor into standby mode. Some video BIOSes reenable interrupts when they are called but do not ensure that a valid interrupt service routine is available. If the video BIOS then generates a hardware or software interrupt while the system is in SMM, in most cases the system will lock up.

3.9 Advanced Power Control (APC)

The BIOS supports APC through the National 87307 Super I/O controller. Two features that have been implemented are Auto Start On AC Loss and Power-On COM1 Ring. Auto Start On AC Loss sets the control for returning to the last known state of the computer, or powering down upon AC power loss to the motherboard. Power-On COM1 Ring sets the control for allowing the computer to be powered on upon an incoming POTS call to a telephony device configured for operation on COM1.

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