Networks of workstations provide an economic solution for scalable computing because they do not require specialized components. Even though recent advances have shown that it is possible to obtain high bandwidth between applications, interconnect latency remains a serious concern. We present CNI, a cluster network interface that not only provides both low latency and high bandwidth but also efficiently supports multiple programming paradigms. This is done by functionally coupling the network adaptor board more closely to the CPU without changing the standard workstation architecture. CNI results in performance gains for applications, substantially reducing communication overhead and delay.