SAN JOSE, Calif. — Dual-core Opteron processors from Advanced Micro Devices and the Infiniband interconnect surged forward in the latest list of the world's top 500 supercomputers posted Monday (Nov. 13). They gained ground lost by Intel processors and Gbit Ethernet interconnects that have dominated the list in the last two years.

AMD chips were used in 113 supercomputers, or 22 percent of those on the latest list, up from just 11 percent a year ago ago. Intel CPUs took their biggest decline ever, slumping from a high of use in 333 systems or a year ago to 261 or 52 percent of systems on the current list.

AMD gained an edge by beating Intel to market with dual-core CPUs. But Intel is catching up with its dual-core Xeon processors already appearing on the current list. In addition, Intel launched on Monday its first quad-core Xeon CPUs and expects to ship as many as 1 million of them before AMD ships its quad-core Opterons.

"Intel processors have only come to dominate the list in the last two to three years. Their use in 66 percent of systems a year ago was quite a high level, so its only natural that might decline," said Erich Strohmaier, a researcher at Lawrence Berkeley National Laboratory and one of the authors of the list.

Stohmaier said Intel's dual-core Woodcrest processor already appears in a number of systems in the current list and will be popular in high-performance computing because the CPU can issue two add or multiple instructions in a single cycle.

"If Intel leapfrogs AMD in quad core, that could drive change in the list over the next six to twelve months. I imagine Intel's share will stabilize or even grow again," Stohmaier said.

The number of systems using AMD's Opteron surpassed the number using IBM Power processors. Power appeared in 93 systems, or 18.6 percent of the computers, up from 73 systems or 14.6 percent one year ago.

Stohmaier said he expects the number of Intel- and AMD-based systems on the list will grow while the number of Power systems will decline. That's because only IBM uses Power CPUs, and one of its three Power families is shrinking in market share, he added.