The SX-9 is a NEC SX supercomputer built by NEC Corporation. The SX-9 Series implements an SMP system in a compact node module and uses an enhanced version of the single chip vector processor that was introduced with the SX-6. The NEC SX-9 processors run at 3.2 GHz, with eight-way replicated vector pipes, each having two multiply units and two addition units; this results in a peak vector performance of 102.4 gigaFLOPS. For non-vectorized code, there is a scalar processor that runs at half the speed of the vector unit, i.e. 1.6 GHz. Up to 16 CPUs and 1 terabyte of memory may be used in a single node. Each node is packaged in an air-cooled cabinet, similar in size to a standard 42U computer rack. The SX-9 series ranges from the single-node SX-9/B system with 4 CPUs to the maximum expansion stage with 512 nodes, 8,192 CPUs, and 970 TFLOPS peak performance. There is up to 4 TB/s shared memory bandwidth per node and 2×128 GB/s node interconnect bandwidth. The operating system is NEC's SUPER-UX, a Unix-like OS.

The SX-9 had the world's fastest vector CPU core.^[1][2] A fully equipped system with 512 nodes would have been the world's fastest supercomputer at the time of release in the first quarter of 2008, with a performance of 819 TFLOPS. The SX-9 was discontinued in 2015.^[3]

The German national meteorological service (DWD) operated two independent SX-9 clusters, with 976 processors, 31,232 GB of RAM and 98 TFLOPS performance in total.^[4]