IBM has maintained its lead, and its bragging rights, over rivals in the number of supercomputer systems it operates throughout the world.

IBM holds a 47.8 percent share of the biannual Top500 Supercomputers list to be released Tuesday at Supercomputing 2006, an industry convention in Tampa, Fla. Second-place Hewlett-Packard holds a 31.2 percent share of systems on the list.

The Top500 list, compiled by university researchers in the United States and Germany, ranks supercomputer systems by performance as measured by teraflops, or trillions of computer calculations per second.

But even though supercomputer end users don’t buy them for their energy efficiency, the Top500 will begin to include power efficiency measures in its next list, due out in June 2007. In recent years, energy and the labor costs of managing computer systems have exceeded the cost of the hardware itself.

"We are looking at teraflops per watt, and we are starting to track that and will at least provide the numbers," said Erich Strohmaier, a staff scientist at Lawrence Berkeley National Laboratory in California, and one of the list compilers. However, next year’s list will still be ranked by computing performance.

Rankings based on processor brand shifted significantly with Advanced Micro Devices’ Opteron processors taking market share from Intel processors. Intel’s market share fell to 52.2 percent from 66.6 percent in the survey a year ago, while AMD’s doubled to 22.6 percent from 11 percent. IBM fell to third place despite seeing its share rise to 18.6 percent from 14.6 percent.

IBM claims the number-one spot on the 500 list with its IBM BlueGene/L system, installed at the U.S. Department of Energy’s (DOE) Lawrence Livermore National Laboratory in California. It operates at a maximum processing speed of 280.6 Tflops per second.

Supercomputing capabilities have been growing faster than Moore’s Law, said Jack Dongarra, a distinguished professor in the Innovative Computing Laboratory at the University of Tennessee at Knoxville, another one of the list creators. Moore’s Law holds that computer processing power doubles every 18 months, but the supercomputing sector’s has been doubling every 14 months.

Dongarra cited developments such as multiple core processing, enabling chips to handle several instructions simultaneously, and Gigabit Ethernet, moving data among a network of computers at 1 billion bits per second, for the surge in supercomputing power.

The aggregate processing power of all 500 systems on the latest list is 3.54 petaflops (Pflops), from 2.79 Pflops in the June listing and 2.3 Pflops a year ago. A petaflop is 1,000 teraflops.