The current release of mpich does not support hetrogenous Linux clusters. Since all Linux systems are identified as LINUX by the p4 layer, attempts to start processes will all try to run the same executable which will fail. It is possible to work around this, but not pretty. This has been reported upstream as #3895. It will be fixed when the p4 layer is rewritten. --- Begin /etc/mpich/machines.LINUX (modified conffile) damiel zebulon--- End /etc/mpich/machines.LINUX