The latest rankings from the Green500 list of the world's greenest high-performance computers (HPCs) finds IBM holding sway as the leading provider of the most energy-efficient supercomputers in the world.

The company holds 18 out of 20 of the top spots, including the top ranking for its BladeCenter QS22 Cluster at the University of Warsaw's Interdisciplinary Centre for Mathematical and Computational Modeling. Similar configurations of that HPC also landed in a two-way tie for 2nd place as well as 4th place.

Those rankings, coupled with IBM's Blue Gene/P Solution HPC system hold on 14 of the top 20 positions in the ranking, means that IBM has dominated the list of the greenest supercomputers in the world.

The remaining two HPCs in the top 20 included the GRAPE-DR accelerator Cluster at the National Astronomical Observatory of Japan in fifth place, and the NEC HPC 140Rb-1 Cluster at the University of Stuttgart, Germany, in 20th place.

The Green500 is a twice-yearly ranking of the most energy-efficient HPCs around the globe. The list, which measures megaflops (the number of computing operations per second) per watt used, parallels the Top500, a list of the most powerful HPCs regardless of energy use.

Rankings on this year's list find a muddled combination of performance and energy efficiency: the number one most-powerful HPC on the list, an IBM BladeCenter QS22/LS21 Cluster at the DOE's Los Alamos National Laboratories, ranks fourth on the Green500 list. The University of Warsaw's top-ranked energy-efficient computer places a lowly 422 on the Top500 for overall computing performance.

Some key trends from the makers of the Green500 list:
• The overall efficiency of supercomputers continues to improve. While the supercomputers on the Green500 are collectively consuming more power, they are using the power more efficiently than before.
• Commodity processors continue to nip at the heels of previous-generation custom processors.
• For the first time, maximum energy efficiency remains the same, but three 500-Mflops/Watt supercomputers drop out of the Green500.
In a statement celebrating the company's victories, IBM's vice president of deep computing, David Turek, said, "Modern supercomputers can no longer focus only on raw performance. To be commercially viable these systems most also be energy efficient. IBM has a rich history of innovation that has significantly increased energy efficiency of our systems at all levels of the system that are designed to simultaneously reduce data center costs and energy use."

The list of the top 20 greenest HPCs is below; the full list is available online at Green500.org.
Green500 Rank MFLOPS/W Site* Computer* Total Power (kW) TOP500 Rank*
1 536.24 Interdisciplinary Centre for Mathematical and Computational Modeling, University of Warsaw BladeCenter QS22 Cluster, PowerXCell 8i 4.0 Ghz, Infiniband 34.63 422
2 458.33 DOE/NNSA/LANL BladeCenter QS22/LS21 Cluster, PowerXCell 8i 3.2 Ghz / Opteron DC 1.8 GHz, Infiniband 138 61
2 458.33 IBM Poughkeepsie Benchmarking Center BladeCenter QS22/LS21 Cluster, PowerXCell 8i 3.2 Ghz / Opteron DC 1.8 GHz, Infiniband 138 62
4 444.94 DOE/NNSA/LANL BladeCenter QS22/LS21 Cluster, PowerXCell 8i 3.2 Ghz / Opteron DC 1.8 GHz, Voltaire Infiniband 2483.47 1
5 428.91 National Astronomical Observatory of Japan GRAPE-DR accelerator Cluster, Infiniband 51.2 277
6 371.67 ASTRON/University Groningen Blue Gene/P Solution 94.5 124
7 371.67 IBM - Rochester Blue Gene/P Solution 126 84
7 371.67 IBM Thomas J. Watson Research Center Blue Gene/P Solution 126 85
7 371.67 Max-Planck-Gesellschaft MPI/IPP Blue Gene/P Solution 126 86
7 371.67 Bulgarian State Agency for Information Technology and Communications (SAITC) Blue Gene/P Solution 63 245
7 371.67 Moscow State University Blue Gene/P Solution 63 246
7 371.67 Oak Ridge National Laboratory Blue Gene/P Solution 63 247
7 371.67 Stony Brook/BNL, New York Center for Computational Sciences Blue Gene/P Solution 63 248
14 368.89 EDF R&D Blue Gene/P Solution 252 36
15 368.3 IDRIS Blue Gene/P Solution 315 24
16 367.4 King Abdullah University of Science and Technology Blue Gene/P Solution 504 14
17 366.58 DOE/NNSA/LLNL Blue Gene/P Solution 1134 9
18 363.98 Forschungszentrum Juelich (FZJ) Blue Gene/P Solution 2268 3
19 363.98 Argonne National Laboratory Blue Gene/P Solution 1260 7
20 273.06 HWW/Universitaet Stuttgart NEC HPC 140Rb-1 Cluster, Xeon X5560 2.8Ghz, Infiniband 186 77