Distributed processing ethernet switch with adaptive cut-through switching

A packet switching system includes at least two network cards (100). Each network card receives data packets via a plurality of associated ports. The switching system also includes a system card (200) and an interconnect (20) for connecting the system card to the network cards. Each one of the network cards comprises a plurality of network controllers (110) for sending and receiving packets to and from a corresponding port. The network cards also comprise a packet processor (130) for buffering packets received by the network controllers and sending destination addresses of the received packets to the system card via the interconnect, for receiving forwarding information from the system card, and for forwarding the packets in response to the forwarding information. The network cards also comprise a controller bus (105) for connecting the network controllers to the packet processor and a port controller (115) for coordinating communications between the packet processor and the network controllers over the controller bus.