Intel D15343-003 General Description of Supported CPU States, General Description of Acpi States

Intel® 82854 Graphics Memory Controller Hub (GMCH)

7.1General Description of Supported CPU States

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 and reduces the processor's power consumption. The processor can service snoops and maintain cache coherency in this state.

C2 (Stop Grant): To enter this low power state, STPCLK is asserted. The processor can still service snoops and maintain cache coherency in this state.

C3 (Sleep or Deep Sleep): In these states the processor clock is stopped. The GMCH assumes that no Hub interface cycles (except special cycles) will occur while the GMCH is in this state. The processor cannot snoop its caches to maintain coherency while in the C3 state. The GMCH will transition from the C0 state to the C3 state when software reads the Level 3 Register. This is an ACPI defined register but BIOS or APM (via BIOS) can use this facility when entering a low power state. The Host Clock PLL within the GMCH can be programmed to be shut off for increased power savings and the GMCH uses the DPSLP signal input for this purpose.

C4 (Deeper Sleep): The C4 state appears to the GMCH as identical to the C3 state, but in this state the processor core voltage is lowered. There are no internal events in GMCH for the C4 state that differ from the C3 state. (The C4 state is not supported by the Intel Celeron M Processor, or Genuine Intel Processor).

7.2General Description of ACPI States

Internal Graphics Adapter:

•D0 Full on, display active

•D1 Low power state, low latency recovery. No display, system memory retained

•D3 Hot - All state lost other than PCI config. system memory lost (optionally)

•D3 Cold - Power off

CPU:

•C0 Full On

•C1 Auto Halt

•C2 Stop Clock. Clk to CPU still running. Clock stopped to CPU core.

•C3 Deep Sleep. Clock to CPU stopped.

•C4 Deeper Sleep. Same as C3 with reduced voltage on the CPU.

System States:

•G0/S0 Full On

•G1/S1-MPower On Suspend (POS). System Context Preserved

•G1/S2Not supported.

•G1/S3Suspend to RAM (STR). Power and context lost to chipset.

•G1/S4Suspend to Disk (STD). All power lost (except wakeup on ICH4-M)

•G2/S5Soft off. Total reboot.

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