Supercheap Supercomputer 

Illinois researchers make US $50 000 cluster from Sony Playstations and
off-the-shelf software 

The same hardware that lets millions of gamers race cars or battle giants
may soon allow physicists to probe the foundations of reality. Researchers
at the National Center for Supercomputing Applications and the computer
science department at the University of Illinois in Urbana-Champaign have
created a cluster of Sony Playstation 2 game consoles [photo] for just US
$50 0000, hijacking specialized graphics hardware for scientific
supercomputing. 

One of the researchers, Mike Showerman, explains why the Playstation 2 had
caught their eye after Sony Corp. released a Linux kit for the console last
year. "We saw a potential at such a low cost that we decided that it
was just something that we should be playing around with," Showerman
told IEEE Spectrum. With the kit, users can install the popular Linux
open-source operating system, turning each console into a general-purpose,
network-ready computer. So, the researchers used the kit to network the
consoles together and, more importantly, get access to each Playstation's
sophisticated graphics hardware. This can process as many as 66 million
polygons a second, which is what allows the Playstation to render realistic
3-D worlds so well. For mathematical reasons, each polygon vertex is
represented as a vector, an array of numbers with four elements that
represent positional information. At the heart of the Playstation's
graphics hardware is a pair of "vector units"_dedicated
arithmetic processors designed to operate on vectors. 

"You can use them for generalized matrix-matrix and matrix-vector
calculations by building up software libraries" from the arithmetic
performed on the four-term vectors, says Craig Steffen, another researcher
on the project. Many scientific problems are tackled using vectors and
matrices. 

Developing these libraries is the main focus of the current research.
Ultimately, it would allow specialized physics software for things like
quantum chromodynamics computation to run on the cluster by replacing
normal mathematical software libraries with software libraries designed for
the graphics hardware. But there are a number of obstacles. One is the
problem of developing a more efficient way to move data in and out of the
vector units. "We're going to have to see what tricks we can play with
the hardware," says Steffen. Another is that the vector units do not
fully comply with IEEE 754, the standard for hardware computation of
floating-point arithmetic. 

Ultimately, the purpose of the university's Playstation 2 effort is to
prepare for the 2005 release of the Playstation 3. The hope is that if
useful scientific computation can be demonstrated on the current system,
there will be a road map for the Playstation 3, which will feature even
more powerful graphics hardware, still at a fraction of a PC's cost.  
---Stephen Cass 



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