The SAMOS workshop is an international gathering of highly quali?ed rese- chers from academia and industry, sharing in a 3-day lively discussion on the quietandinspiringnorthernmountainsideofthe MediterraneanislandofSamos. As a tradition, the workshop features plenary presentations in the morning, while after lunch all kinds of informal discussions and nut cracking gatherings take place. The workshop is unique in the sense that not only solved research problems are presented and discussed, but also (partly) unsolved problems and in-depth topical reviews can be unleashed in the scienti?c arena. Consequently, the workshopprovidesthe participantswithanenvironmentwherecollaboration rather than competition is fostered. This fourth edition of the SAMOS workshop developed into a highly int- esting event with a program that consisted of 36 paper presentations as well as a keynote speech by Kees Vissers from Xilinx Research. The paper authors r- resented 12 di?erent countries, the USA, UK, Canada, Brazil, Germany, France, Spain, Finland, Belgium, Portugal, Greece and The Netherlands. The presen- tions were divided into three tracks: recon?gurable computing, architecture and implementation, and system modeling and simulation. We believe that all three tracks showed high-quality, state-of-the-art research in their respective ?elds. Besides the papers from SAMOS IV, this proceedings also features num- ous papers from the SAMOS III workshop. As the SAMOS III edition did not have a well-established proceedings mechanism, we decided to give the authors from last year's edition the opportunity to formally publish their papers in this proceedings.