This book constitutes the refereed proceedings of the 23rd International Conference on Architecture of Computing Systems, ARCS 2010, held in Hannover, Germany, in February 2010. The 20 revised full papers presented together with 1 keynote lecture were carefully reviewed and selected from 55 submissions. This year's special focus is set on heterogeneous systems. The papers are organized in topical sections on processor design, embedded systems, organic computing and self-organization, processor design and transactional memory, energy management in distributed environments and ad-hoc grids, performance modeling and benchmarking, as well as accelerators and GPUs.