AMD is still widely used at the top end of the HPC spectrum often due to interconnect performance.

Pumping out a sustained 1.64 quadrillion mathematical calculations per second (1.64 petaflops) after a recent technological overhaul, the Cray XT Jaguar is now the world's latest fastest supercomputer (huge disclaimer coming) for non-classified research. And once you see what's under the hood, you'll know why.

The system is powered by 45,000 quad-core AMD Opteron processors that take advantage of 362 terabytes of memory. This and other underlaying architecture allows processors to chew on 284 gigabytes of data per second with its impressive I/O bandwidth, which has apparently been a major bottleneck in supercomputers of yesteryear. Information is stored on 750 terabytes of hard drives.

The Cray XT Jaguar can be found at the Department of Energy's Oak Ridge National Laboratory where it will create scientific breakthroughs during the day, and succumb to Crysis at night. [ORNL and EurkeAlert]

http://gizmodo.com/5084224/cray-xt-jaguar-the-new-worlds-fastest-supercomputer

http://www.science.doe.gov/ascr/ProgramDocuments/Docs/Breakthroughs_2008.pdf

http://www.eurekalert.org/pub_releases/2008-11/ddoe-dor111008.php

Jaguar uses over 45,000 of the latest quad-core Opteron processors from AMD and features 362 terabytes of memory and a 10-petabyte file sys¬tem. The machine has 578 terabytes per second of memory bandwidth and unprec¬edented input/output (I/O) bandwidth of 284 gigabytes per second to tackle the biggest bottleneck in leading-edge systems—moving data into and out of processors.