Abstract. While standard processors achieve supercomputer performance, a performance gap exists between the interconnect of MPP's and COTS. Standard solutions like Ethernet can not keep up with the demand for high speed communication of todays powerful CPU's. Hence, high speed interconnects have an important impact on a cluster's performance. While standard solutions for processing nodes exist, communication hardware is currently only available as a special, expensive non portable solution. ATOLL presents a switched, high speed interconnect, which ful lls the current needs for user level communication and concurrency in computation and communication. ATOLL is a single chip solution, additional switching hardware is not required.