The text is organized as follows: We first provide a summary of the QM/MM methodology adopted in MiMiC, 1 followed by a description of the implementation including aspects related to communication between coupled programs and parallelization of QM/MM interactions. We then provide a description of the test systems used for the benchmarks, which are intended to cover a range of typical system sizes. Following this, we present benchmarks showcasing the parallel performance of the MiMiC-based QM/MM implementation for up to several thousand CPU cores, demonstrating superior scaling performance with respect to the preexisting, tight-coupling QM/MM implementation in the CPMD program. We then go on to show that at a large number of cores, parallel efficiency is mainly exhausted due to serial parts of the main driver in CPMD, thus showing that the loose-coupling scheme adopted in MiMiC does not lead to any significant overhead associated to communication, while providing a much more flexible, system-independent framework.