Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chips as mini Internets

11.04.2012
The data-routing techniques that undergird the Internet could increase the efficiency of multicore chips while lowering their power requirements.

Computer chips have stopped getting faster. In order to keep increasing chips’ computational power at the rate to which we’ve grown accustomed, chipmakers are instead giving them additional “cores,” or processing units.

Today, a typical chip might have six or eight cores, all communicating with each other over a single bundle of wires, called a bus. With a bus, however, only one pair of cores can talk at a time, which would be a serious limitation in chips with hundreds or even thousands of cores, which many electrical engineers envision as the future of computing.

Li-Shiuan Peh, an associate professor of electrical engineering and computer science at MIT, wants cores to communicate the same way computers hooked to the Internet do: by bundling the information they transmit into “packets.” Each core would have its own router, which could send a packet down any of several paths, depending on the condition of the network as a whole.

At the Design Automation Conference in June, Peh and her colleagues will present a paper she describes as “summarizing 10 years of research” on such “networks on chip.” Not only do the researchers establish theoretical limits on the efficiency of packet-switched on-chip communication networks, but they also present measurements performed on a test chip in which they came very close to reaching several of those limits.

Last stop for buses

In principle, multicore chips are faster than single-core chips because they can split up computational tasks and run them on several cores at once. Cores working on the same task will occasionally need to share data, but until recently, the core count on commercial chips has been low enough that a single bus has been able to handle the extra communication load. That’s already changing, however: “Buses have hit a limit,” Peh says. “They typically scale to about eight cores.” The 10-core chips found in high-end servers frequently add a second bus, but that approach won’t work for chips with hundreds of cores.

For one thing, Peh says, “buses take up a lot of power, because they are trying to drive long wires to eight or 10 cores at the same time.” In the type of network Peh is proposing, on the other hand, each core communicates only with the four cores nearest it. “Here, you’re driving short segments of wires, so that allows you to go lower in voltage,” she explains.

In an on-chip network, however, a packet of data traveling from one core to another has to stop at every router in between. Moreover, if two packets arrive at a router at the same time, one of them has to be stored in memory while the router handles the other. Many engineers, Peh says, worry that these added requirements will introduce enough delays and computational complexity to offset the advantages of packet switching. “The biggest problem, I think, is that in industry right now, people don’t know how to build these networks, because it has been buses for decades,” Peh says.

Forward thinking

Peh and her colleagues have developed two techniques to address these concerns. One is something they call “virtual bypassing.” In the Internet, when a packet arrives at a router, the router inspects its addressing information before deciding which path to send it down. With virtual bypassing, however, each router sends an advance signal to the next, so that it can preset its switch, speeding the packet on with no additional computation. In her group’s test chips, Peh says, virtual bypassing allowed a very close approach to the maximum data-transmission rates predicted by theoretical analysis.

The other technique is something called low-swing signaling. Digital data consists of ones and zeroes, which are transmitted over communications channels as high and low voltages. Sunghyun Park, a PhD student advised by both Peh and Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor of Electrical Engineering, developed a circuit that reduces the swing between the high and low voltages from one volt to 300 millivolts. With its combination of virtual bypassing and low-swing signaling, the researchers’ test chip consumed 38 percent less energy than previous packet-switched test chips. The researchers have more work to do, Peh says, before their test chip’s power consumption gets as close to the theoretical limit as its data transmission rate does. But, she adds, “if we compare it against a bus, we get orders-of-magnitude savings.”

Luca Carloni, an associate professor of computer science at Columbia University who also researches networks on chip, says “the jury is always still out” on the future of chip design, but that “the advantages of packet-switched networks on chip seem compelling.” He emphasizes that those advantages include not only the operational efficiency of the chips themselves, but also “a level of regularity and productivity at design time that is very important.” And within the field, he adds, “the contributions of Li-Shiuan are foundational.”

Sarah McDonnell | EurekAlert!
Further information:
http://www.mit.edu

More articles from Information Technology:

nachricht New software speeds origami structure designs
12.10.2017 | Georgia Institute of Technology

nachricht Seeing the next dimension of computer chips
11.10.2017 | Osaka University

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>