The hardware transactional memory (HTM) implementations in commercially available processors are significantly hindered by their tight capacity constraints. In practice, this renders current HTMs unsuitable to many real-world workloads of in-memory databases. This paper proposes SI-HTM, which stretches the capacity bounds of the underlying HTM, thus opening HTM to a much broader class of applications. SI-HTM leverages the HTM implementation of the IBM POWER architecture with a software layer to offer a single-version implementation of Snapshot Isolation. When compared to HTM- and software-based concurrency control alternatives, SI-HTM exhibits improved scalability, achieving speedups of up to 300% relatively to HTM on in-memory database benchmarks.