"The conservative Parallel DEVS protocol offers a novel approach that allows conservative simulation of DEVS-based PDES systems. The protocol is based on the classical Chandy-Misra-Bryant synchronization mechanism, and it extends the DEVS abstract simulator to provide means for lookahead computation and null-messages. We present a purely conservative simulator, called CCD++, designed for running large-scale DEVS and Cell-DEVS models in parallel and distributed fashion. A comparative performance analysis is presented, analyzing the performance of CCD++ compared to an optimistic DEVS simulator. Several DEVS-based environmental models with different characteristics are studied. The experiments indicate that the conservative simulator improves performance in terms of execution time, memory usage, operational cost, and system stability for very large models."--From the paper.