RHiNET-2/SW is a network switch for the RHiNET-2 parallel computing system. RHiNET-2/SW enables high-speed and long-distance data transmission between PC nodes for parallel computing. In RHiNET-2/SW, a one-chip CMOS switch-LSI and eight pairs of 800-Mbit/s 12-channel parallel optical interconnection modules are mounted into a single compact board. This switch allows high-speed 8-Gbit/s/port parallel optical data transmission over a distance of up to 100 m, and the aggregate throughput is 64 Gbit/s/board. The CMOS-ASIC switching LSI enables high-throughput (64 Gbit/s) packet switching with a single chip. The parallel optical interconnection modules enable high-speed and low-latency data transmission over a long distance. The structure and layout of the printed circuit board is optimized for high-speed, high-density device implementation to overcome electrical problems such as signal propagation-loss and crosstalk. All of the electrical interfaces are composed of high-speed CMOS-LVDS logic (800 Mbit/s/pin). We evaluated the reliability of the optical I/O port through long-term data transmission. No errors were detected during 50 hours of continuous data transmission at a data rate of 800 Mbit/s 10 bits (BER: < 2.44 10-14). This test result shows that RHiNET-2/SW can provide high-throughput, long-transmission-length, and highly reliable data transmission in a practical parallel computing system.