Scalable POWERparallel (SP) is a series of supercomputers from IBM. SP systems were part of the IBM RISC System/6000 (RS/6000) family, and were also called the RS/6000 SP. The first model, the SP1, was introduced in February 1993, and new models were introduced throughout the 1990s until the RS/6000 was succeeded by eServer pSeries in October 2000. The SP is a distributed memory system, consisting of multiple RS/6000-based nodes interconnected by an IBM-proprietary switch called the High Performance Switch (HPS). The nodes are clustered using software called PSSP, which is mainly written in Perl.