Supercomputers that mix CPUs with graphics processors made their mark on the Green500 list of top energy-efficient supercomputers released this week.
Eight of the world's greenest supercomputers combined specialised accelerators like GPUs with CPUs to boost performance and make supercomputers more power efficient, according to the Green500 list, which is released twice a year. The list was released by the same group that compiles the Top500 list.
Supercomputers with accelerators are three times more energy efficient than their non-accelerated counterparts on the list, according to Wu Feng, associate professor of electrical and computer engineering at Virginia Polytechnic Institute and State University's college of engineering.
Two of the top eight green supercomputers are new entrants from China, and combine graphics processors from Nvidia with Intel's CPUs. In the previous list issued in November, only one supercomputer combined CPUs with GPUs from Advanced Micro Devices, but that machine has now dropped to the 11th spot.
The Green500 list is compiled to "ensure that supercomputers only simulate climate change and not create it", according to the Green500 website.
The list rates the greenest supercomputers by measuring performance in relation to power consumed. The calculation takes the megaflops-per-second performance (MFLOP/s) of a supercomputer and divides it by per watt of energy consumed. Supercomputers with accelerators averaged 554 MFLOP/s per watt, while other measured supercomputers without accelerators produced 181 MFLOP/s per watt.
The supercomputers combining GPUs with CPUs include the Dawning Nebulae supercomputer, which was in the fourth spot, and the Mole-8.5 supercomputer, which took the eighth spot. The supercomputers are in China and combine Nvidia's Tesla C2050 graphics processors with Intel's Xeon X5650 quad-core processor, which runs at 2.66GHz. The Nebulae supercomputer achieved efficiency of around 492.64 MFLOP/s per watt, while the Mole-8.5 achieved efficiency of 431.88 MFLOP/s per watt.
The top three green supercomputers were IBM supercomputers, all in Germany. The supercomputers include PowerXCell 8i processors from IBM, with custom field-programmable gate array accelerators to boost application performance. The supercomputers were also the top three in the previous list issued in November.
Overall, IBM chips were used in six of the top eight green supercomputers.
There is growing interest in building supercomputers that use graphics processors along with CPUs. GPUs are typically faster than traditional CPUs at executing certain tasks, such as those used in scientific and computing applications. Some institutions like the Tokyo Institute of Technology have announced plans to deploy more GPUs in an effort to squeeze more performance out of servers.