While transactional memory (TM) research on shared-memory chip multiprocessors has been flourishing over the last years,limited research has been conducted in the cluster domain. In this paper,we introduce a research platform for exploiting software TMon clusters. The distributed software transactional memory (DiSTM) system has been designed for easy prototyping of TM coherence protocols and it does not rely on a software or hardware implementation of distributed shared memory. Three TM coherence protocols have been implemented and evaluated with established TM benchmarks. The decentralized transactional coherence and consistency protocol has been compared against two centralized protocols that utilize leases. Results indicate that depending on network congestion and amount of contention different protocols perform better.