Multi-core technology produces a new scenario for communicating processes in an MPI cluster environment and consequently the involved trade-offs need to be uncovered. This motivation guided our research and lead to a new approach for setting up more efficient clusters built with commodities. Thus, alternatively to the utilization of non-commodity interconnects such as Myrinet and Infiniband, we present a proposal based on leaving cores idle relatively to application processing in order to build economically more accessible clusters of commodities with higher performance. Execution of fine-grained IS algorithm from NAS Parallel Benchmark revealed a speedup of up to 25%. Interestingly, a cluster organized according to the proposed setup was able to outperform a single multi-core SMP host in which all processes communicate inside the host. Therefore, empirical results indicate that our proposal has been successful for medium and fine-grained algorithms.