IBM’s Roadrunner supercomputer narrowly beat out a revamped Cray XT Jaguar high-performance computer system to hold onto the No. 1 spot on the latest version of the Top 500 Supercomputer list.

According to the Top 500 list, which was released Nov. 17, the IBM Roadrunner system held onto the top spot with a performance of 1.105 petaflops, or more than 1.1 quadrillion calculations per second. The IBM Roadrunner system was installed at the U.S. Department of Energy’s Los Alamos National Laboratory in New Mexico. It was the first supercomputer to break the petaflop mark.

The Cray XT Jaguar supercomputer, which was recently upgraded for the DOE’s Oak Ridge National Laboratory in Tennessee, placed second with a performance of 1.059 petaflops.

The Top 500 Supercomputer list is released twice each year and is compiled by researchers at the University of Mannheim in Germany, the National Energy Research Scientific Computing Center at the Lawrence-Berkeley National Laboratory and the University of Tennessee. The group uses the Linpack Benchmark as the standard to measure the performance of each supercomputer.

The latest version of the Top 500 list was released just before the start of the 2008 Supercomputing Conference in Austin, Texas.

Earlier this month, researchers at the Oak Ridge laboratory issued a statement that reported that the Cray Jaguar system was faster than the IBM Roadrunner supercomputer. However, the rankings of the Top 500 list are determined by how each supercomputer performs in relation to the Linpack Benchmark.

While IBM and Cray made history with breaking the petaflop mark this year, the latest version of the list shows how powerful supercomputers are becoming in just a short time. The entry-level performance mark for the Top 500 list increased from 9 teraflops to 12.64 teraflops in just six months.

Although it missed out on the top spot, Cray managed to place four systems within the Top 10 of the Top 500 list. IBM had three systems listed within the Top 10, and Sun Microsystems, SGI and Dawning each placed one supercomputer in the Top 10.

Intel processors are now the dominant chips used for the Top 500. All together, Intel processors are used within 379 different supercomputers, while Advanced Micro Devices’ processors are used in 59 systems. The IBM Power processor is used in 60 supercomputers.

While IBM and Cray dominate the list of most powerful systems, Hewlett-Packard builds more systems in the Top 500 list than any other HPC vendor. This version of the Top 500 included 209 systems built by HP.

The United States continues to dominate the Top 500 list and especially the Top 10. According to this version of the Top 500, nine out of the top 10 systems are located in the United States, and seven of those supercomputers belong to the DOE. The only Top 10 system not located in the United States is the Dawning 5000A, which is housed at the Shanghai Supercomputer Center in China.

The next version of the Top 500 list will be released in June 2009.