Can the world's most powerful computers also be green? That was the underlying question behind a 2007 ranking of the world's supercomputers which compares the number of floating-operations they can perform per second versus the amount of energy consumed, or "FLOPS per watt."
The Green 500 list compiled by researchers at Virginia Tech is intended to
draw attention to idea that designers of supercomputers should pay more
attention to the energy consumption, not just speed or computational
"In the world of supercomputers, the thinking has traditionally
focused entirely on performance," says Virginia Tech associate
professor Wu Feng, who spearheaded the Green 500 project with Kirk
Cameron. "No one has worried about the power being consumed. Well, the
world has changed. There is a lot of concern right now about the amount
of power being consumed by computers and data centers in general, and
we felt it was time to do something that really challenged the thinking
of the (supercomputer) establishment."
In fact, as manufacturers have pursued the goal of building
supercomputers that can complete hundreds of trillions of
floating-point operations per second they have inadvertently created
computers that consume so much energy and produce so much heat they
require elaborate cooling systems to ensure their proper operation.
The first Green 500 list will be
refined in the months and years ahead, adds Feng. Initially, not all
companies with computers on the Supercomputer 500 ranking would or
could provide energy consumption metrics for their machines. However,
based on the feedback received to date, and the attention the Green 500
is generating, Feng believes the list will be more comprehensive in the
future and the methodology more refined.
The top of 2007's list is dominated by IBM's Blue Gene
supercomputers. In fact, IBM had nine out of 10 of the top 10 sites.
The only non-IBM installation to crack the top 10 was a Dell PowerEdge
cluster at Stanford University. In terms of flops per watt, the top
installation was an IBM Blue Gene supercomputer installed at the
Science and Technology Facilities Council Daresbury Laboratory in
Cheshire, England. It achieves 357.23 megaflops per watt.
Much of IBM's success is due to the use of more efficient
processors. The new generation of Blue Gene supercomputers use 850 MHz
CPUs compared to 2GHz CPUs used in most supercomputers.
While this is the Green 500's first year, the genesis for the list
dates back to 2001 when Feng was working at the Los Alamos National
Laboratory. He was struggling to maintain the reliability of a
supercomputer installed at the laboratory, which was overheating due to
the high number of power-hungry processors.
That led him to design a new supercomputer, which focused as much on
energy efficiency as power. The result was a machine named Green
Destiny, which used 240 Transmeta processors, operating at 667 MHz, and
sipped only 3.2 kilowatts of power (about the same as two hair dryers).