For the first time, an Intel-based system has topped the Green500 list, an achievement made possible through the use of the new Intel Xeon Phi co-processor launched this week at SC12.

Green500 was established in 2007 and ranks high performance computers in terms of energy efficiency: performance per watt.

The latest Green500 List was released today (http://www.green500.org/lists/green201211) and the top spots on the list have been taken over by machines that combine commodity processors with coprocessors or graphics processing units (GPUs) to form heterogeneous high-performance computing systems.

The record-breaking computer, called Beacon, belongs to the National Institute for Computational Sciences (NICS). NICS is a well-known center in high-performance computing, established in partnership with the University of Tennessee and Oakridge National Lab (ORNL). The system achieves 2.5 billion floating point operations per section for each Watt of power consumed (2.5 Gigaflops/W).

Employing Intel's Sandy Bridge series of Xeon central processing units (CPUs) and four of Intel's Xeon Phi coprocessors per node Beacon achieved a peak 112,200 gigaflops of performance running the LINPACK benchmark while consuming only 44.89 kW of power.

The Intel Xeon Phi--"Knights Corner"-- is a 22nm multicore coprocessor featuring the world's first 3D Tri-Gate transistors. Like its GPU counterparts, the Intel Xeon Phi resides on a PCI Express board that plugs into a machine's expansion slots. However, unlike its GPU-based cousins, the Xeon Phi architecture provides a more tightly coupled instruction path for developers and delivers better energy efficiency.

Rounding out the top five systems are three other machines using GPU accelerators combined with traditional AMD or Intel CPUs.

"Metaphorically, think of CPU-GPU systems operating like the human brain, where the CPU could be viewed as the left brain and the GPU as the right brain," says Dr. Wu Feng, founder of the Green500 List. "Each side of the brain is suited to process different types of tasks." In second place is the SANAM system from the King Abdulaziz City for Science and Technology, an Intel CPU system that uses AMD's new FirePro S10000 GPU accelerators, and in third and fourth are the Titan and Todi systems by Cray that employ AMD Opteron CPUs and nVIDIA Tesla K20 GPU accelerators. In number five is the previous Green500 List number one system, IBM's Blue Gene/Q that uses PowerPC BQC CPUs. All of these systems are over two gigaflops per watt.

Overall, the performance of machines in the Green500 List has increased at a higher rate compared to power consumption. "That's why the machines' efficiencies are going up," says Feng. "We are more performance for the same amount of power." For machines based on commodity components--machines built with off-the-shelf components-- coprocessors and GPUs are attributing a great deal to the efficiency gains. So much so that they are keeping pace and in the latest list even outpacing purpose built systems like IBM's Blue Gene/Q. "Power consumption is still going up," says Wu, and that is still a concern.