In a Department of Energy deal worth $325 million, IBM will build two massive supercomputers called Sierra and Summit that combine a new supercomputing approach from Big Blue with Nvidia processing accelerators and Mellanox high-speed networking. The companies and US government agency announced the deal on Friday ahead of a twice-yearly supercomputing conference that begins Monday. The show focuses on the high-end systems that are used to calculate car aerodynamics, detect structural weaknesses in airplane designs and predict the performance of new drugs.