Intel 317443-001US Power Measurement Support, Transition to S3, Transition to S4, P= V 2 R

Theory of Operation—Intel®945GME Express Chipset

3.6.1Transition to S3

If enabled, the transition to S3 from the full-on state can be accomplished in the following ways:

•The OS performs the transition through software.

•Press the front panel power button for less than four seconds (assuming the OS power management support has been enabled).

Note: The power button is accessed by adding a switch to the pins 5 and 6 on the front panel header J8J1.

3.6.2Transition to S4

“Wake on S4” (Suspend to disk) is controlled by the operating system.

3.6.3Transition to S5

The transition to S5 is accomplished by the following means:

•Press the front panel power button for less than four seconds (if enabled through the OS).

•Press the front panel power button for more than four seconds to activate power button override.

3.6.4Transition to Full-On

The transition to the Full-On state can be from S3 or S5. The transition from S3 is a low latency transition that is triggered by one of the following wake events:

•Power management timer expiration

•Real Time Clock (RTC) triggered alarm

•Power button activation

•USB device interrupt

•ICH7M pin PME# assertion

•AC power loss

For AC power loss, the system operation is defined by register settings in the Intel ICH7-M. Upon the return of power, a BIOS option, set prior to the power loss, allows the system to either go immediately to the S5 state, or reboot to the Full-On state, no matter what the state was before the power loss. External logic for this functionality is not necessary. If the BIOS remains in the S5 state after AC power loss, only the power button or the RTC alarm can bring the system out of the S5 state. The status of enabled wake events will be lost.

3.7Power Measurement Support

Power measurement resistors are provided on the platform to measure the power of most subsystems. All power measurement resistors have a tolerance of 1%. The value of these power measurement resistors are 2 mΩ by default. Power on a particular subsystem is calculated using the following formula:

P= V 2 R

	Intel® CoreTM 2 Duo processor with the Mobile Intel® 945GME Express Chipset
May 2007	Manual
Order Number: 317443-001US	31