82374EB datasheet(187/208 Pages) INTEL

187 / 208 page

82374EB82374SB

130 POWER MANAGEMENT (82374SB)

The ESC has extensive power management capability permitting a system to operate in a low power state

without being powered down In a typical desktop personal computer there are two statesPower On and

Power-Off Leaving a system powered on when not in use wastes power The ESC provides a Fast OnOff

feature that creates a third state called Fast Off (Figure 33) When in the Fast Off state the system consumes

less power than the Power-On state

The ESC’s power management architecture is based on three functionsSystem Management Mode (SMM)

Clock Control and Advanced Power Management (APM) Software (called SMM code) controls the transitions

between the Power On state and the Fast Off state The ESC invokes this software by generating an SMI to

the CPU (asserting the SMI

signal) A variety of programmable events are provided that can generate an

SMI The SMM code places the system in either the Power On state or the Fast Off state

A Fast On event is an event that instructs the computer (via an SMI to the CPU) to enter the Power-On state in

anticipation of system activity by the user Fast On events are programmable and include moving the mouse

pressing a key on the keyboard an external hardware event an incoming call to a system FAXModem a RTC

alarm or the operating system

290476 – E0

Figure 33 Fast OnOff Flow

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82374EB Datasheet(PDF) 187 Page - Intel Corporation