Dissecting the Latest TOP and Green500

The latest list of the top 500 supercomputers, which was announced on June 22, had few surprises for TOP500 watchers. China's Tianhe-2 computer retained the top spot with a performance of 33.86PFLOPS on the Linpack benchmark, and the US Department of Energy's Titan computer, located at Oak Ridge National Laboratory, came in second with 17.59PFLOPS peek performance.
Thirty-seven systems came in at higher than 1PFLOPS, up from 31 systems in the last version of the list. HP built the most systems on the list (182), followed by IBM with 176 and Cray at a distant third with 50 systems. The US is home to the highest number of systems by a large margin (233), although the US total is down from 265 systems the last list six months ago. (If you like statistics, note that the rest of the world now has more than half of the 500 total systems.)
Also announced was the Green500 list, which ranks the efficiency of supercomputers in MFLOPS/watt. The philosophy of the Green500 is that a truly advanced system will not just deploy a huge number of cores but will actually extract the maximum computing power per unit of electrical power.
The TSUBAME-KFC system at the Tokyo Institute of Technology topped off the Green500 list and was the only system with an efficiency exceeding 4,000MFLOPS/watt. The top 17 spots were all occupied by systems that use heterogeneous architectures – with GPUs and/or co-processors as well as conventional CPUs. The Green500 site stresses that the prevelance of heterogeneous designs is not found throughout the list but is concentrated in the upper ranks.  Interestingly, the fastest computer in the world – China's Tianhe-2, which tops the TOP500 list – is also the 49th most efficient computer in delivering cycles per unit of electrical power.
Because the limiting factor in supercomputers is often the power supply and cooling capability, the Green500 list highlights new technologies that could one day lead to advances for the giant systems of the TOP500 list.