Scientist links PCs to run at 'super' speed

Roldan Pozo was tired of waiting for supercomputer time at the National Institute of
Standards and Technology.

So with $30,000, the NIST research scientist strung together three PCs and built his
own supercomputer to run complex math calculations.

"Most projects like this one start out with some people wanting to build a fast
computer," said Pozo, a scientist in NIST's Mathematical and Computational Sciences
Division. "But we had real work to get done."

Pozo built the supercomputer with off-the-shelf hardware and software. Scientists in
his division use it to investigate high-performance computations such as numerical linear
algebra. He said anyone could follow his basic formula to build a cheap supercomputer.

Pozo, an avid jazz fan, named his creation JazzNet. By linking three Pentium Pros via
Fast Ethernet, Pozo built a system that achieved speeds of 1 billion floating-point
operations per second for some applications.

And JazzNet can easily hold its own against workstations, Pozo said. The JazzNet home
page at lists
some of the benchmark tests Pozo used to measure JazzNet performance.

On some tests, such as the 3-D Helmholtz Solver for which a computer has to manipulate
color images, JazzNet beat workstations by more than a minute. On the Helmholtz test,
JazzNet completed the task in 14 seconds. A 32-node Connection Machine 5 from Thinking
Machines Corp. of Bedford, Maine, completed the same task in 12 seconds, and a Sun
Microsystems Sparcstation 20 took 82 seconds.

Besides raw computing speed, Pozo said, the advantage of a personal supercomputer is
that users don't have to share the machine.

"Even if a supercomputer can run an application in a few seconds, what you don't
see is how long the program sat in line waiting for computing time," Pozo said.

"With JazzNet, I have it in my office ready whenever I need it," he said.

JazzNet's three nodes are separate processors. Node 1 is a new 200-MHz Pentium Pro quad
processor motherboard with an interleaved 256-bit memory bus. Node 2 is a dual 200-MHz
Pentium Pro board with 256M of RAM. And Node 3 is a single 200-MHz Pentium Pro board with
128M of RAM. The third PC supports an SVGA monitor that Pozo uses to monitor JazzNet's

Pozo built JazzNet with three processor types to test each one's effectiveness.
Surprisingly, the single-processor PC worked best, Pozo said.

"There is a trade-off. The more processors you have, the more computational power
you have," he said. "But each processor is sharing a bus to memory, and it gets
more and more difficult to feed them."

Quad processors can plug away at massive amounts of data, but if the system cannot feed
enough data to the processors, they sit idle, he said.

Pozo said there is a point of diminishing returns at which multiple processors do not
increase a system's power.

Cost also favors using single-processor PCs. "The quad-processor machines are more
expensive than a single-processor machine, and by more than a factor of four," he
said. "A single-processor node is running at about $2,000. The four-processor boards
are about $10,000 or $15,000."

Pozo plans to soup up JazzNet by adding nine more single-processor PCs.

He linked the PCs using Fast EtherLink 10Base-T network interface cards from 3Com Corp.
of Santa Clara, Calif.

JazzNet runs Red Hat Software Inc.'s Linux operating system. The Research Triangle,
N.C., company's OS is similar to Unix, which Pozo said was a real plus because most of the
NIST scientists use Unix.

And Linux can handle multiple machines on a single network better than other systems he
experimented with, Pozo said.

Another advantage to JazzNet is easy system maintenance. When a Fast EtherLink card
went bad, Pozo walked across the street to a computer store and bought a new card.

A few minutes later, JazzNet was back online.

About the Author

John Breeden II is a freelance technology writer for GCN.

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