The Cray-based supercomputer built for Sandia National Laboratories in Albuquerque, many of whose 26,544 processors are actually AMD Opteron 2.4 GHz dual-cores, leapt from the #9 to the #2 spot on the semi-annual list of the Top 500 performing supercomputers, published this week by the University of Mannheim in association with Berkeley National Laboratory and the University of Tennessee, Knoxville.

Twice each year, the rankings of 500 of the world's supercomputers are judged by their maximal observed peak performance, in gigaflops (GFlops, or billions of floating-point operations per second). This performance is called the "R_max rating," although Mannheim does publish theoretical mean performance as a comparison.

This time, IBM's BlueGene/L becomes the four-time champion, with an R_max rating of 280,600, equivalent to its performance score last June, and retaining a commanding lead. With 131,072 processors -- almost five times as many as the Cray/AMD-based Red Storm -- surmounting BlueGene/L may be about as probable for other computers as beating Gerry Kasparov in chess once was for other humans.

But AMD continues to make a strong go of it. In the November rankings, AMD x86 and x64 processors are included in 113 of the Top 500 systems, up from 80 last June. Opteron single-core processors were prominent in 37 of these, and dual-cores in the other 76, including Red Storm, which registered an R_max rating of 101,400 GFlops, up from 38,180 last June.

Dual-core Opterons also helped AMD seize the #9 spot -- within a Sun Fire cluster at the Tokyo Institute of Technology -- and teamed with Cray to take the #10, #15, and #16 slots.

The count for Intel-based systems was noticeably down this time, with 109 EM64T-based supercomputers (down from 118 in June), 119 Itanium 32-bit units (down from 147) and 35 IA-64-based units (down from 37). EM64Ts helped Intel and Dell collectively take the #6 slot: Sandia Labs' Thunderbird, with an even R_max score of 53,000, along with the #11, #12, #20, and #27 slots. An Itanium 64-based unit running at the French atomic energy agency took the #7 slot, with an R_max score of 52,840.

Meanwhile, IBM's Power processors, including POWER5s, POWER4s, and the original PowerPC, took 91 slots, the highest being #1, of course. This time, though, the Thomas J. Watson Research Center's venerable Power-based BlueGene BGW was bumped from the #2 perch by AMD and Cray, to #3.

Linux was the operating system powering 408 of the Top 500 supercomputers, up from 391 last time, including 27 of the top 30 units. The best performing Mac OS X system came in at #28, a homemade consolidation including Apple Xserve clusters at the private consultancy COLSA Corp., with an R_max score of 16,180.

Macintosh technology was also featured in #47 and #160. And for the first time in recent memory, there were no Windows machines -- zero -- in the Top 500, with the final two having been bumped off of June's list. NCSA, which had been running the highest-ranking Windows system on the list, has since switched over to all-Linux.