Datasheet
Functional Description
136 Intel
®
82845G/82845GL/82845GV GMCH Datasheet
4.6 Power and Thermal Management
4.6.1 Power Management Support Overview
• ACPI Supported
• System States: S0, S1(desktop), S3, S4, S5, C0, C1, C2 (desktop)
• Graphics States: D0, D3
• Monitor States: D0, D1, D2, D3
4.6.2 Processor Power State Control
• C0 (Full On): This is the only state that runs software. All clocks are running, STPCLK# is
deasserted and the processor core is active. The processor can service snoops and maintain
cache coherency in this state.
• C1 (Auto-Halt): The first level of power reduction occurs when the processor executes an
Auto-Halt instruction. This stops the execution of the instruction stream. The processor can
service snoops and maintain cache coherency in this state.
• C2 (Stop Grant): The next level of power reduction occurs when the processor is placed into
the Stop Grant state by the assertion of STPCLK#. The GMCH supports only the Stop Grant
state in C2.
4.6.3 Sleep State Control
• S0 (Awake): In this state all power planes are active.
• S1 (Stop Grant): S1 state is the same as C2 state (Stop Grant).
• S3 (Suspend-To-RAM): The next level of power reduction occurs when the clock synthesizer
and main power planes (ICH4, GMCH, and the processor) are shut down but the DRAM
memory plane and the ICH4 resume well remain active. This is the Suspend-To-RAM (STR)
state. All clocks from the synthesizer are shut down during the S3 state.
• S4 (Suspend-To-Disk) and S5 (Soft Off): The next level of power reduction occurs when the
memory power is shut down in addition to the clock synthesizer, ICH4, GMCH, and the
processor power planes. The ICH4 resume well is still powered.
• G3 (Mechanical Off): In this state only the RTC well is powered. The system can only
reactivate when the power switch is returned to the “on” position.
4.6.4 Graphics Adapter State Control
• D0 (Active): In this state, power planes are normal and active. This is the normal on state for
the GMCH graphics functions. The GMCH graphics functions enter this state out of power-on-
reset.
• D3 (Inactive): The D3 power state is the lowest power mode. Displays are off, and the
registers and memory need not be maintained. HSYNC and VSYNC are not pulsed in this
state.