The da Vinci Research Kit (dVRK) is an open-source and open-hardware surgical robotics research platform that provides complete access to all levels of control on decommissioned da Vinci Surgical Systems. The original dVRK, released to the research community in 2012 and now installed at more than 40 institutions worldwide, is based on the first-generation da Vinci system. We present dVRK-Si, an update that extends support to decommissioned second/third generation da Vinci S/Si patient-side robots. We describe extensions to the system architecture that maintain compatibility and interoperability with the original dVRK system, thereby enabling a heterogeneous mix of dVRK and dVRK-Si arms in the same system.