The described embodiments include a system that modulates the width of a high-speed link. The system includes a transmitter circuit coupled to a high-speed link that includes N serial lanes. During operation, while using a first number of lanes to transmit frames on the high-speed link, the transmitter circuit determines a second number of lanes to be used to transmit frames on the high-speed link based on a bandwidth demand on the high-speed link. The transmitter circuit then sends an indicator of the second number of lanes to a receiver on the high-speed link. Upon receiving an error-free acknowledgment of the indicator from the receiver, starting from a predetermined frame, the transmitter circuit transmits subsequent frames on the high-speed link using the second number of lanes.