[FoRK] 64-core mesh from Tilera

Eugen Leitl <eugen at leitl.org> on Mon Aug 20 01:35:59 PDT 2007

http://www.technologyreview.com/printer_friendly_article.aspx?id=19269

Monday, August 20, 2007

A New Design for Computer Chips

An MIT spinoff introduces the first commercial chip with a mesh architecture.

By Kate Greene

Today, MIT spinoff Tilera announced that it's shipping a computer chip with
64 separate processors whose design differs drastically from that of the
chips found in today's computers. The new chip, called Tile64, avoids some of
the speed bottlenecks inherent in today's chip architecture, and it can
operate at much lower power, says Anant Agarwal, founder and chief technology
officer of Tilera, based in Santa Clara, CA. Initially, Tile64 will be used
in video applications such as videoconferencing systems, and in network
hardware that monitors traffic to reduce e-mail spam and viruses.

Chips with multiple processing units, or "cores," are nothing new. But by
allowing the cores to communicate directly with each other, Tilera has
addressed a widespread concern about the viability of adding more cores to
microprocessors. "Every processor in the market today is a multicore," says
Agarwal. "The hope of the industry is to double the number of cores every 18
months. My prediction is, by 2014, we will have 1,000-core architectures. But
the problem is, [current] architectures don't scale."

In existing multicore chips, each core communicates with the others via a set
of wires called a bus. Performance doesn't necessarily suffer when two or
four cores share a bus, but when 16 or more cores try to use it
simultaneously, data can get backed up. Agarwal explains that Tilera's chip
has no central bus. Instead, each core is connected to all the others. Also
on each core is a full-featured processor, which can run an operating system,
and memory caches, which hold data that needs to be quickly accessed.

In effect, the Tile64 has a mesh structure that's similar to that of the
Internet, a network in which there are many decentralized nodes. One reason
the Internet is able to pass around data so quickly is that packets of
information are sent through a vast network and can avoid traffic jams. If
everyone's e-mail had to go through a central server, there would undoubtedly
be delays. Tilera's microprocessor, says Agarwal, "is very much like the
Internet on a chip." And like the Internet, Tilera's chip can be scaled up
gracefully; it doesn't need to be redesigned each time new cores are added.

The idea of using mesh architecture for multicore chips has been explored for
at least a decade, in research labs at MIT, Stanford, and the University of
Texas, Austin. And recently, Intel announced a prototype 80-core chip based
on a mesh. But Tilera is the first company to offer a product that uses the
new architecture.

"Having a lot of cores is good, but they must be able to communicate with
each other at high data rates," says Jerry Bautista, codirector of Intel's
terascale-computing research program. "There are advantages to using a mesh
... You can deal with traffic jams pretty easily." Bautista says that Intel
researchers are trying to find the best way to implement mesh
architectures--among other experimental designs--in future chips. But he also
cautions that making massively multicore systems work efficiently isn't as
simple as redesigning the hardware.

"We believe that to really get the most use out of these many-core systems,
there's going to be quite a significant modification to the way people
program today," Bautista says. The cores can handle many different
instructions at once, he says, and software engineers will have to learn new
programming techniques to take full advantage of the added computational
capacity.

Tilera's Agarwal says that his company has addressed that concern by
providing a software environment that helps customers gradually upgrade,
debug, and optimize their applications to work on the 64-core system--even
applications designed to run on a single core.

The company's technology is being presented this week at the Hot Chips
symposium at Stanford, in Palo Alto. Nathan Brookwood, founder of Insight64,
an analysis firm, says that many people at the conference are excited about
Tilera's work, mainly because it could have immediate applications, such as
expanding the capacity of videoconferencing systems and analyzing network
traffic in routers. "I think they have a potential winner here," says
Brookwood.

Intel's Bautista says the marketplace may be ready for a chip with more
computing power, but it would need to be low power and easily programmed. He
says that Intel will keep an eye on Tilera, as it does on many startups that
are first to market with new technologies, to see how customers respond and
which aspects of the technology could be improved. "We use companies like
this to help us test the waters," he says.


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