operating a data link with a host in a flow control unit (FLIT) mode using fixed-sized packets, the data link being in a partial width link state (PLS) in which a first set of lanes of the data link are in an electrical idle state and a second set of lanes of the data link are in an active state available for data traffic with the host;

detecting, using an inactivity timer, low traffic or inactivity on one or more lines of the second set of lanes; and

transitioning, in response to detecting the low traffic or inactivity, the one or more lines of the second set of lanes from the PLS to a partial width standby link state (PSLS) without handshaking between the host and the endpoint, in the PSLS the one or more lines of the second set of lanes being in a standby state that has lower power consumption than the active state.