Dynamically modulating link width

An apparatus comprising:

• a local port having control logic to receive from a remote port a remote width capability during a link initialization, the remote width capability to correspond to the remote port and including a plurality of supported link widths and corresponding lane identifiers, compare the remote width capability to a local width capability of the local port, select a common link map that the remote port and the local port can support, and operate a link between the local port and the remote port at a plurality of link widths in accordance with the remote width capability without an additional link initialization or negotiation between the local port and the remote port, wherein the control logic is to establish a first link width for the link based on the remote width capability and the local width capability, select a second link width based on the remote width capability and an operating condition of the local port and modulate the link to the second link width, the second link width to be narrower than the first link width when the operating condition is a power saving condition, the control logic to place a portion of the local port in a low power state after modulating the link to the second link width, and the second link width to be wider than the first link width when the operating condition is an increased bandwidth condition, the control logic to bring a portion of the local port out of a low power state before modulating the link to the second link width.

A system comprising:

• a remote port;
• a unidirectional link coupled to the remote port;
• and
• a local port coupled to the link, the local port including control logic to receive from the remote port training data of a training sequence including a remote width capability from the remote port during a link initialization, the remote width capability to correspond to the remote port and including a plurality of supported link widths and corresponding lane identifiers, operate the link at a plurality of link widths in accordance with the remote width capability without an additional link initialization or negotiation between the local port and the remote port, including establishment of a first link width for the link and selection of a second link width responsive to an operating condition change of the local port, modulate the link to the second link width, thereafter detect an empty transaction queue of the local port associated with an active part of the link, and based on the determination of the empty transaction queue place an active link portion of the local port in an intermediate power state, wherein a reactivation latency time of the intermediate power state is smaller than a reactivation latency time of a low power state.

A method comprising:

• receiving from a remote port training data including a remote width capability during a link initialization between a local port and the remote port, the remote width capability corresponding to the remote port and including one or more supported link widths and corresponding lane identifiers;
• establishing a first link width for a link based on the remote width capability and a local width capability;
• selecting a second link width based on the remote width capability and an operating condition of the local port, wherein the selecting includes:
• selecting the second link width to be narrower than the first link width, the operating condition including a power saving condition, and placing a portion of the local port in a low power state after modulating the link to the second link width, the low power state having a relatively long reactivation latency;
• and
• selecting the second link width to be wider than the first link width, the operating condition including an increased bandwidth condition, and bringing a portion of the local port out of the low power state before modulating the link to the second link width;
• modulating the link to the second link width without an additional link initialization or negotiation between the local port and the remote port;
• detecting an empty transaction queue associated with an active portion of the local port;
• and
• placing the active portion in an intermediate power state, the intermediate power state having a shorter reactivation latency than a reactivation latency of the low power state.