Using systems with varying sizes of QM and MM regions, we provide benchmarks and per-formance studies for MiMiC interfacing between the plane wave/pseudopotential CPMD program as a main MD driver with the classical MD package GROMACS, thus enabling both Born-Oppenheimer (BO) and Car-Parrinello (CP) QM/MM MD to be performed. The CPMD program provides a preexisting, tight-coupling QM/MM interface to GROMOS; 4 its choice as a main driver therefore allows for a direct comparison of the performance of looseand tight-coupling strategies.