Supercomputers take efficiency up another notch
RISC cores and hybrids deliver most flops per watt
GPU co-processors are going to have to have a dramatic leap in performance in the same thermal envelope and the overhead of talking across the PCI-Express bus is going to have to be lowered for GPUs to compete. And the word from SC10 from both Nvidia and Advanced Micro Devices is that they are going to give massively cored machines like BlueGene/Q a serious run for their supercomputing money.
The third most energy-efficient super on the Green500 list doesn't have a lot of flops, but the EcoG super installed at the National Center for Supercomputing Applications does downshift to dual-core Core i3 processors running at 2.93 GHz to manage the Nvidia C2050 GPU co-processors in the cluster, eliminating lots of heat from the CPU side. The machine was rated at 33.6 teraflops, but burned 36 kilowatts of juice, for a power rating of 933.1 megaflops per watt.
Another prototype machine, the Fujitsu-designed K super going into Japan's Riken Advanced Institute for Computational Science, ranked fourth on the Green500. Formerly known as Project Keisoku and originally intended to scale up to 10 petaflops using a mix of vector processors made by NEC and Hitachi and scalar processors made by Fujitsu, the entire machine is now being built only using Fujitsu's eight-core "Venus" Sparc64-VIIIfx processors and a 6D interconnect called Tofu. (NEC and Hitachi backed out of the $1.2bn Project Keisoku in May 2009, saying they would lose money on the deal if they proceeded.)
Fujitsu started building what is now called the K supercomputer back in September. The prototype of the K super is not powerful enough to make the Top 500 list, but using 2 GHz Sparc64-VIIIfx processors the machine delivers 828.7 megaflops per watt and that is better than a slew of supers based on IBM's PowerXCell 8i processors, which have dominated the Green500 list for several years.
Three Cell-based clusters running at the Forschungszentrum Juelich lab in Germany and at the Universities of Regensburg and Wuppertal (also in Germany) deliver 773.4 megaflops per watt and are tied for fifth place on the Green500 list. But these machines are a dead end, because IBM is no longer making Cell processors for use in its BladeCenter blade servers.
Three ceepie-geepie machine round out the top 10 of the Green500 list, with a cluster made by Super Micro for the University of Frankfurt using quad-core Opterons and ATI Radeon graphics cards as GPU co-processors coming in at 740.8 meaflops per watt with the eight rank. Number nine on the Green500 list is a cluster at the Georgia Institute of Technology which pairs two-socket cookie-sheet servers from Hewlett-Packard (using six-core Xeon 5600 processors) with Nvidia GPUs; it is rated at 63.9 teraflops (117th on the Top 500 list) delivers 677.1 megaflops per watt. Number 10 on the Green500 list is a Xeon-C2050 cluster at the National Institute for Environmental Studies in Japan, which ranked 102 on the Top 500 list with 74.8 teraflops of sustained Linpack performance and which delivered 636.4 megaflops per watt.
Energy efficiency continues to improve because of the pressure on supercomputer makers to not only deliver more flops, but to take a lot less energy to do it. In the inaugural Green500 list back in November 2007, all of the top 10 machines on the list were BlueGene/L or BlueGene/P supers with the BlueGene/L machines coming in at 210.6 megaflops per watt and the BlueGene/P machines ranging from 310.9 through 357.2 megaflops per watt. In June 2008, Cell-based machines and the Roadrunner Opteron-Cell hybrid at the Los Alamos National Laboratory took over the top three spots on the Green500 list, jumping ahead of the BlueGene/P boxes and ranging from 437.4 to 488.1 megaflops per watt.
More Cell-based supers were added to the top of the Green500 list, pushing above 536.2 megaflops per watt in the November 2008 list, and in June 2009, nothing much else changed at the top except the Grape-DR FPGA hybrid at the national Astronomical Observatory in Japan came in with 428.9 megaflops per watt.
The prototype Tiahne-1 Xeon-Radeon cluster was the first ceepie-geepie to break the top ten on the Green500 a year ago, with a rating of 379.2 megaflops per watt. The Nebulae ceepie-geepie cluster at the National Supercomputing Center in Shenzhen, China, was number four on the Green500 list from June 2010, at 492.6 megaflops per watt. Interestingly, on the June 2010 list, there were two Xeon-Nvidia GPU hybrids in the top 10 and six machines lashing together x64 processors and Cell co-processors. There were only two plain-vanilla x64-based clusters on the list on the current November Green500 list: IBM's BlueGene/Q prototype and Fujitsu's K prototype. All of the others are based on Cell or x64-GPU hybrids. ®
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