This book constitutes the refereed proceedings of the 25th International Conference on Architecture of Computing Systems, ARCS 2012, held in Munich, Germany, in February/March 2012.The 20 revised full papers presented in 7 technical sessions were carefully reviewed and selected from 65 submissions. The papers are organized in topical sections on robustness and fault tolerance, power-aware processing, parallel processing, processor cores, optimization, and communication and memory.