The impact of Gigabit networking with Myrinet 2000 hardware and MPICH-GM software on a 2-way SMP Beowulf-Class cluster for parallel unstructured adaptive mesh refinement using the PYRAMID library is described. Network performance measurements show that approximately 225 Mbytes/s (1.8 Gbits/s) with 9.3μ seconds latency can be achieved for large messages in ping-pong tests. The performance varies depending on how processors communicate; either within an SMP node or across nodes. When applied to parallel unstructured AMR of 3D tetra-hedral meshes noticeable improvement is observed when compared to 100BaseT (100 Mbits/s) Ethernet. Furthermore, when compared to traditional systems, such as the SGI Origin 2000, one realizes that Beowulf-Clusters with fast networks and high performance SMP processors compare favorably with such systems—even for communication intensive applications.