A publication of the Advanced Simulation & Computing Division, NA-121.2, NNSA Defense Programs
September 2008
NA-ASC-500-08—Issue 8
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ASC’s Roadrunner Supercomputer Energy Efficient
In addition to breaking the petaFLOPS record, the Roadrunner supercomputer located in Los Alamos is #3 on the June 2008 Green500 list (http://www.green500.org/lists/2008/06/green500.php).
To illustrate the dramatic improvements in power efficiency, the first vector supercomputer installed at Los Alamos in 1976 needed 115 kW to deliver about 100 megaFLOPS on highly optimized matrix operations hand-coded in assembly language. To match Roadrunner's performance, ten million such machines would require 1,150,000 megaWatts of power — more than the entire electricity-generating capacity of the United States.
Power efficiency of the fastest computers in the world has increased more than 500,000-fold. The Roadrunner system delivers record-breaking 1.026 petaFLOPS while using only 2.345 megaWatts of power, an important advantage since construction of larger facilities would have been costly and time consuming. In addition, significant savings in operating costs are enabled by Roadrunner's power efficiency of 437 megaFLOPS/Watt, more than double that of the #2 machine on the TOP500 list.
Roadrunner uses power efficient PowerXCell 8i processors in IBM's QS22 Cell Blades, which can reach up to 488 megaFLOPS/Watt. Each Cell chip contains two kinds of processor cores to perform the computational work and the overall coordination. Roadrunner also benefits from IBM's LS21 Opteron processor blades, which are less power efficient but enable less computationally intensive code to run without modifications. Roadrunner combines advantages of three kinds of processor cores in a hybrid system, each of which is programmed in a high-level language such as C or FORTRAN.
The Roadrunner supercomputer
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