When you enter the computer room on the second floor of Tokyo Institute of Technology's computer building, you're not immediately struck by the size of Japan's second-fastest supercomputer. You can't see the Tsubame computer for the industrial air conditioning units that are standing in your way, but this in itself is telling. With more than 30,000 processing cores buzzing away, the machine consumes a megawatt of power and needs to be kept cool.
Tsubame was ranked 29th-fastest supercomputer in the world in the latest Top 500 ranking with a speed of 77.48T Flops (floating point operations per second) on the industry-standard Linpack benchmark.
While its position is relatively good, that's not what makes it so special. The interesting thing about Tsubame is that it doesn't rely on the raw processing power of CPUs (central processing units) alone to get its work done. Tsubame includes hundreds of graphics processors of the same type used in consumer PCs, working alongside CPUs in a mixed environment that some say is a model for future supercomputers serving disciplines like material chemistry.
Graphics processors (GPUs) are very good at quickly performing the same computation on large amounts of data, so they can make short work of some problems in areas such as molecular dynamics, physics simulations and image processing.
"I think in the vast majority of the interesting problems in the future, the problems that affect humanity where the impact comes from nature ... requires the ability to manipulate and compute on a very large data set," said Jen-Hsun Huang, CEO of Nvidia, who spoke at the university this week. Tsubame uses 680 of Nvidia's Tesla graphics cards.
Just how much of a difference do the GPUs make? Takayuki Aoki, a professor of material chemistry at the university, said that simulations that used to take three months now take 10 hours on Tsubame.
Tsubame itself - once you move past the air-conditioners - is split across several rooms in two floors of the building and is largely made up of rack-mounted Sun x4600 systems. There are 655 of these in all, each of which has 16 AMD Opteron CPU cores inside it, and Clearspeed CSX600 accelerator boards.