Tokyo Tech develops supercomputer TSUBAME 2.5

TOKYO, JAPAN: Tokyo Tech announced the development of supercomputer TSUBAME 2.5, recently upgraded from 2.0 to 2.5. How does TSUBAME 2.5 differ from K and other supercomputers? The details are described in the February issue of the Tokyo Institute of Technology Bulletin.

Tsubame, swallow in Japanese, is the symbol of Tokyo Institute of Technology (Tokyo Tech). TSUBAME also stands for Tokyo Tech Supercomputer and Ubiquitously Accessible Mass Storage Environment, which is one of the world's top, large-scale supercomputers. TSUBAME 1.0 began operating in 2006 and was the fastest supercomputer in Japan at that time.

In 2010, TSUBAME 2.0 was developed and began operating; its speed measured in petaflops was a first in Japan. (Petaflops is a computer's ability to do one quadrillion floating point operations per second.) TSUBAME 2.0 also achieved world-leading electrical efficiency that earned it a 2010 global rank of No. 2 in the Green500 rankings for supercomputer energy efficiency. TSUBAME was upgraded from 2.0 to 2.5 in the fall of 2013. Specifically, what changed? How is TSUBAME different from K and other supercomputers?

TSUBAME 2.0, which first began operating in November 2010, was the first petaflop supercomputer in Japan, at 2.4 petaflops theoretical performance. The name TSUBAME is known worldwide because at that time it was ranked fourth in the TOP500 performance rankings based on benchmarks of supercomputer processing speed. The GPU is behind this dramatic performance improvement, both when it was first introduced in 2008 in a supercomputer at the Global Scientific Information and Computing (GSIC) Center at Tokyo Tech and also in the current upgrade.

Basically similar to a PC, a supercomputer is organized into a structure with a chip, an electronic part called a CPU, which is equipped with a CPU core (circuits that process computations). When calculations to process and update data resident on the memory chip are repeated, they produce results of simulations as numeric values and images. In recent years, supercomputers have been developed that are capable of a massive parallel use of these CPUs, which significantly raises their computing power.

TSUBAME uses around 17,000 CPU cores. Although each CPU is useful for increasing the speed of word processing among other things, they take up a lot of space and contain many functions that are not often needed by a supercomputer. If these CPUs were laid out side by side, they would fill the area of a gymnasium or in the case of the K supercomputer, exceed 3,000 m2, which is equivalent to the area of a small arena.

Furthermore, their power consumption would be at least 10 megawatts, enough to run 10,000 ordinary households. That is too high. So the question was -- what can be done? ....The GPU came to the rescue. It is a multi-core processor with many computation cores built into one package.

The GPU was originally a semiconductor chip used for processing calculations required for 3D graphics displays. Above and beyond its ability to quickly process image data, it is compact with several hundred to several thousand efficient yet small cores, hence the name multi-core processor.

When these GPUs are utilized within the central processor of a general-purpose supercomputer, they are notable for their superior energy efficiency and space savings. For these reasons, they were used in the first generation TSUBAME and were then even more widely employed in the 2.0 version described above.