We present experimental results for the evaluation of PC clusters that differ on several aspect of their architecture, such as being mono or biprocessors and having a high bandwidth interconnection network or not. These experiments confirm that a good equilibrium between the speed (throughput) of the different components is crucial for a satisfactory performance of such a machine. On the other hand they also show that the latency of the underlying infrastructure is of less importance and can be hidden by applying techniques from coarse grained parallelism.