Abstract: HNI is a high speed network interface adapter designed for the SNOW system. A protocol processor and an ad hoc hardware protocol accelerator are used to speed up the Homer protocol. Furthermore, a part of the DSM protocol and multi user accessing mode are also supported. In this paper, after carefully considering the requirement of the SNOW network, a general structure of HNI is described and then the logic implementation of the adapter is specified. And finally the testing result of the adapter is analyzed.