The AutoHalt Power Down State

Description

Refer to Figure 27-2 on page 688. When a HLT (Halt) instruction is executed, the processor generates a Special transaction (see “The Special Transaction” on page 1306) on the FSB to broadcast a Halt message to the system. It then leaves the Normal state and enters the AutoHalt Power Down state. This state has the following characteristics:

  • The processor powers down all logic except the logic that is necessary for the recognition of interrupts and the snooping of memory accesses generated by other FSB agents.

  • The BCLK signal on the FSB continues to run.

  • The processor services any snoop events (i.e., memory transactions generated by other agents on the FSB) and then returns to the AutoHalt Power Down state. ...

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