A system includes a transmission device and a reception device that are connected through a link. The reception device includes a reception buffer configured to receive and store transaction layer packets and a reception flow controller configured to generate flow control packets by monitoring an occupation state of the reception buffer. The transmission device includes a transmission buffer, a transmission flow controller and a dynamic frequency controller. The transmission buffer stores pending transaction layer packets to be transferred to the reception device. The transmission flow controller controls a flow of transaction layer packets to be transferred to the reception device based on the flow control packets received from the reception device. The dynamic frequency controller controls a frequency of an internal clock signal of the transmission device by monitoring a state of the transmission buffer and a state of the transmission flow controller.