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This is one example of a conservation core developed by UC San Diego computer scientists. The small boxes in the image are the pattern of logic gates that are spatially placed over a small portion of the GreenDroid chip. Credit: UC San Diego Computer Science (CSE)
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A new smartphone chip prototype under development at the University of
California, San Diego will improve smartphone efficiency by making use
of "dark silicon" – the underused transistors in modern microprocessors.
On August 23, UC San Diego computer scientists presented GreenDroid,
the new smartphone chip prototype at the HotChips symposium in Palo
Alto, CA.
Dark
silicon refers to the huge swaths of silicon transistors on today's
chips that are underused because there is not enough power to utilize
all the transistors at the same time. The new GreenDroid chip prototype
from computer scientists at UC San Diego will deliver improved
performance through specialized processors fashioned from dark silicon.
These processors are designed to run heavily used chunks of code, called
"hot code," in Google's Android smartphone platform.
Computer
science professors Michael Taylor and Steven Swanson from the
Department of Computer Science and Engineering (CSE) at the UC San Diego
Jacobs School of Engineering are leading the project.
"This
is an exciting time for UCSD. Our students are designing a real
multicore processing chip, in an advanced technology, that is
simultaneously advancing the state-of-the art in both smartphone and
processor design. This marks the first of what I hope is many such chips
that will come out of the UCSD research community," said Taylor.
The GreenDroid presentation at HotChips caught the attention of IEEE Spectrum, EETimes and LightReading, which all ran stories.
While
chip makers can now make similar types of specialized processors by
hand, the UC San Diego computer scientists developed a fully automated
system. It generates blueprints for specialized processors, called
conservation cores, from source code extracted from applications.
Conservation
cores also incorporate focused reconfigurability that allows them to
adapt to small changes in the target application while still delivering
efficiency gains.
Dark Silicon
This
work is motivated by the growing problem of dark silicon, which refers
to transistors on microprocessors that are forced to remain off most of
the time because of power constraints.
"We
don't have enough power to use all the transistors at once – that is
the 'utilization wall,'" said UC San Diego computer science graduate
student Nathan Goulding who presented the team's GreenDroid chip at
HotChips. Goulding led GreenDroid development, which is one part of the
larger conservation core project.
"The utilization wall will change the way everyone builds processors," the computer scientists reported in their HotChips talk.
If
this utilization wall problem is not solved, more transistors on
computer chips will not necessarily lead to improved performance or
problem solving capacity in each new chip generation.
Automated Hardware Maker
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This is an overview of the GreenDroid project from computer scientists at UC San Diego. Credit: UC San Diego Computer Science (CSE)
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As
a real-world prototype, the computer scientists from the UC San Diego
Jacobs School of Engineering used dark silicon to build specialized
circuits for specific tasks frequently performed by popular smartphone
applications such as Web browsers, email software and music players. The
computer scientists asked 'where does most of the computation happen?'
They took answers to this question, and fed the relevant code into their automated tool chain.
"A
chip that does MP3 decoding…people can build specialized logic for this
by hand, but it's an enormous amount of effort and this doesn't scale
well. Our approach is automated," said Goulding.
The
computer scientists input pieces of code shared by multiple software
applications for Android phones. The output at the end of the automated
chain is a blueprint for specialized hardware. This specialized hardware
will only execute some regions of the software code. The rest of the
code, known as "cold code", is executed by the phone's general
processor.
The
computer scientists chose a smartphone for their chip prototype because
mobile handsets are the new dominant computing platform. "Smartphones
are going to be everywhere," said Goulding, "We said to ourselves,
'let's make a prototype chip that saves energy on Android phones.'"
The HotChips slides and the full list of authors: GreenDroid: A Mobile Application Processor for Silicon's Dark Future
PDF: http://cseweb.ucsd.edu/users/swanson/papers/HotChips2010GreenDroid.pdf.com
Authors:
Nathan Goulding, Jack Sampson, Ganesh Venkatesh, Saturnino Garcia, Joe
Auricchio, Jonathan Babb*, Michael Taylor, and Steven Swanson,
Proceedings of HotChips, 2010. *Jonathan Babb is at CSAIL, Massachusetts
Institute of Technology
Related
work from the team: Conservation Cores: Reducing the Energy of Mature
Computations, Ganesh Venkatesh, Jack Sampson, Nathan Goulding, Saturnino
Garcia, Vladyslav Bryksin, Jose Lugo-Martinez, Steven Swanson, and
Michael Bedford Taylor, ASPLOS '10: Proceeding of the 15th international
conference on Architectural support for programming languages and
operating systems, 2010.
Original article
