82374EB Datasheet, PDF (187/208 Pages) Intel Corporation – SYSTEM COMPONENT (ESC)

82374EB 82374SB
13 0 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 states Power On and
Power-Off Leaving a system powered on when not in use wastes power The ESC provides a Fast On Off
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 FAX Modem a RTC
alarm or the operating system
Figure 33 Fast On Off Flow
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