A computer interface unit for accomplishing a transfer from a transmitting application running on a first computer, having a system bus and a first main memory connected to said system bus, to a receiving application (60b, 60c) running on a second computer (30b, 30c), said transmitting application providing an operating system with transmit virtual addresses of data to be transmitted to said receiving application, said interface unit comprising: A. a mapping memory containing a map of transmit physical addresses in said first main memory corresponding to the transmit virtual address of the data to be transmitted; B. a transmit work queue pointer register directly accessible to said transmitting application and said operating system; wherein the operating system is arranged to: 1. load into said mapping memory the transmit physical addresses corresponding to said transmit virtual addresses, and 2. enter into said transmit work queue pointer register a pointer that points to a transmit work queue (101 a) in the first main memory and wherein each entry in the transmit work queue specifies information associated with the data to be transmitted, said entry including an identification of the transfer, an amount of the data and an identification of a location of each of said transmit virtual addresses in said mapping memory; wherein the interface unit further comprises: means for accessing said first main memory in accordance with said physical addresses contained in said mapping memory to retrieve said data therefrom; and means for transmitting said retrieved data to said receiving application on said second computer. A. a mapping memory containing a map of transmit physical addresses in said first main memory corresponding to the transmit virtual address of the data to be transmitted; B. a transmit work queue pointer register directly accessible to said transmitting application and said operating system; wherein the operating system is arranged to: 1. load into said mapping memory the transmit physical addresses corresponding to said transmit virtual addresses, and 2. enter into said transmit work queue pointer register a pointer that points to a transmit work queue (101 a) in the first main memory and wherein each entry in the transmit work queue specifies information associated with the data to be transmitted, said entry including an identification of the transfer, an amount of the data and an identification of a location of each of said transmit virtual addresses in said mapping memory; wherein the interface unit further comprises: means for accessing said first main memory in accordance with said physical addresses contained in said mapping memory to retrieve said data therefrom; and means for transmitting said retrieved data to said receiving application on said second computer. 1. load into said mapping memory the transmit physical addresses corresponding to said transmit virtual addresses, and 2. enter into said transmit work queue pointer register a pointer that points to a transmit work queue (101 a) in the first main memory and wherein each entry in the transmit work queue specifies information associated with the data to be transmitted, said entry including an identification of the transfer, an amount of the data and an identification of a location of each of said transmit virtual addresses in said mapping memory; means for accessing said first main memory in accordance with said physical addresses contained in said mapping memory to retrieve said data therefrom; and means for transmitting said retrieved data to said receiving application on said second computer.