Nearly every supercomputer runs Linux
Just as with the previous list of the Top500 Supercomputers, the Oak Ridge National Laboratory's Cray XT5 'Jaguar' leads the pack with a sustained performance of 1.76 PFlop/s. However, a new Chinese entrant called Nebulae has achieved a higher peak performance of 2.98 PFlop/s (compared to Jaguar's peak of 2.33 PFlop/s) and is placed second overall.
Of the 187 new entrants, all but one are running some variant of Linux and in fact 470 of the Top 500 run Linux, 25 some other Unix (mostly AIX) and the remaining 5 run Windows HPC 2008.
The Chinese systems Nebulae and 7th placed Tianhe-1 are both based on a hybrid design with each node comprising a pair of Intel Xeon processors attached to a pair of GPUs (NVidia for Nebulae and AMD for Tianhe-1) as accelerators. These two systems helped China to take second place for total PFlop/s (9.2%), still trailing USA with 55.4%.