All Windows PC GAMESS/Firefly versions are parallel but can work in serial (sequential) mode. ... This library defines a particular implementation of MPI the PC GAMESS will use. At present, there are the following dlls available in the BINDINGS folder of PC GAMESS/Firefly installation directory: . ... The recommended MPI implementation for PC GAMESS/Firefly running in parallel on self-made (non CCS-based) Windows clusters is NT-MPICH. ... Parallel Windows Instructions: NT-MPICH . ...