This study proposes asynchronous MPI, a simple and effective parallel programming model for SMP clusters, to reimplement the High PerformanceLinpack benchmark. The proposed model forces processors of an SMP node to work in different phases, thereby avoiding unneccessary communication and computation bottlenecks. As a result, we can achieve significant improvements in performance with a minimal programming effort. In comparison with a de-facto flat MPI solution, our algorithm can yield a 20.6% performance improvement for a 16-node cluster of Xeon dual-processor SMPs.