Blue Gene/L, the fastest supercomputer in the world, has broken its own speed record, reaching 135.5 teraflops - a trillion calculations a second.

That is double the speed it clocked up to take it to the number one spot in the Top 500 supercomputer league.

The IBM Blue Gene machine that achieved the new mark is being assembled for the Lawrence Livermore National Laboratory, a US Department of Energy (DOE) lab.

Blue Gene's new record was achieved by doubling the number of current racks to 32. Each rack holds 1,024 processors, yet the chips are the same as those found in high-end computers on the High Street.

The processors are special dual-processing engines, known as cores.

The final machine will help scientists work out the safety, security and reliability requirements for the US's nuclear weapons stockpile, without the need for underground nuclear testing.

The worlds top 5 supercomputers are:
1. Blue Gene/L, USA
2. Columbia, USA
3. Earth Simulator, Japan
4. MareNostrum, Spain
5. Thunder, USA