IBM's Blue Gene is still the world's fastest supercomputer, but sites running on HP and Silicon Graphics equipment are starting to close the gap. 

This is according to twice-yearly Top500 list of the world's fastest supercomputers, which shows that the number one position has once again been claimed by the BlueGene/L System, a joint development of IBM and the Department of Energy's (DOE) National Nuclear Security Administration (NNSA) and installed at DOE's Lawrence Livermore National Laboratory.
Although this particular installation has occupied the top position since November 2004, it has has been significantly expanded and now achieves a Linpack benchmark performance of 478,2 TeraFlops (trillions of calculations per second), compared to 280,6 TeraFlops six months ago.
Coming in at number two is a new installation of the same type of IBM machine. It is a BlueGene/P system installed in Germany at the Forschungszentrum Juelich (FZJ) and it achieved performance of 167,3 TeraFlops.
The contender at number three is not only new, but also the first system for a new supercomputing center, the New Mexico Computing Applications Center in Rio Rancho. The system, built by SGI and based on the Altix ICE 8200 model, posted a speed of 126,9 TeraFlops.
For the first time ever, India placed a system in the top 10. The Computational Research Laboratories installed a Hewlett-Packard Cluster Platform 3000 BL460c system. They integrated this system with their own innovative routing technology and achieved 117,9 TeraFlops performance.
The number five place is also a new Hewlett-Packard Cluster Platform 3000 BL460c system and installed at a Swedish government agency. It was measured at 102,8 TeraFlops.
In the Top500 rankings, multi-core processors are the dominant chip architecture. The most impressive growth showed the number of systems using the Intel Clovertown quad core chips which grew in six months from 19 to 102 systems. The majority of remaining systems uses dual core processors.
A total of 354 systems (70,8%) now use Intel processors. This is up from six months ago (289 systems, 57,8 %) and represents the largest share for Intel chips in the Top500 ever.
The AMD Opteron family, which passed the IBM Power processors a year ago, remained the second most common processor family with 78 systems (15,6%), down from 105 systems (21%) six months ago; 61 systems (12,2%) use IBM Power processors, down from 85 systems (17%) six months ago.
A total of 406 systems are labeled as clusters, making this the most common architecture in the Top500 with a stable share of 81,2%.
Gigabit Ethernet is still the most-used internal system interconnect technology (270 systems) due to its widespread use by industrial customers, followed by InfiniBand technology with 121 systems.
The US is clearly the leading consumer of HPC systems with 284 of the 500 systems. The European share (149 systems – up from 127) is still rising and is again larger then the Asian share (58 – down from 72 systems).