Hi Based on the documentation ( http://www.gromacs.org/Documentation/Cut-off_schemes), it seems that, with GMX 5, GBSA implicit solvent simulations with infinite cutoff (rcoulomb = 0, rvdw = 0, pbc = no) cannot be done on GPUs. Is that right? For CPU simulations I am quite happy with 4.6.5! Best Sandeep