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PCI Express System Architecture by MindShare, Inc, Ravi Budruk, Don Anderson, Tom Shanley

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Software Initiated Link Power Management

When software initiates configuration write transactions to transition the power state of a device to conserve power, devices must respond by transitioning their link to the corresponding low power state.

D1/D2/D3Hot and the L1 State

The specification requires that when all functions within a device have been placed into any of the low power states (D1, D2, or D3hot) by software, the device must initiate a transition to the L1 state. A device returns to L0 as a result of software intitiating a configuration access to the device or due to a device initiated Power Management Event (PME). See Figure 16-21.

Figure 16-21. Devices Transition to L1 When Software Changes their Power Level from D0

Upon receiving ...

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