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ARM Keynote: Will ‘Dark Silicon’ Derail The Mobile Internet?

Comments(0)Filed under: Industry Insights, ARM, low power, Mobile, Dark Silicon

Dark Silicon sounds like it should be the title of a best-selling thriller novel, and in a way, it is a thriller when it comes to the future of semiconductors. Will advanced nodes produce a huge mass of transistors that will go "dark" because we can't afford to power them? Will all our dreams about a more intelligent Internet come to a crashing halt because of this unforeseen problem?

These provocative questions were raised by Mike Muller, ARM CTO, at the March 25 EE Times "Designing with ARM" virtual conference. Co-sponsored by Cadence, the one-day event also included panels, chats, and virtual exhibit booths.

Redefining the mobile Internet

Muller's keynote didn't go to the "dark side" right away. He first painted an optimistic picture of what the mobile Internet could be like in another ten years. Muller envisioned a time in which clients will have power, complexity, and performance that's equivalent to high-end servers today. These clients could be embedded in any device - digital picture frames, smart energy meters, printers, you name it. "The Internet will no longer be seen as servers," he said. "It will become the software platform that defines what will be run on the client."

Cloud computing will define the software platform, Muller said. Software that is "programmed from the cloud, and communicated from the cloud, is going to transform what the pervasive Internet is all about." As a result, he said, a lot of today's "static" consumer products will gain Internet capability in way that will transform the functionality they offer.

The dark lining behind the clouds

But there's "trouble in paradise up in the clouds," Muller said. And that trouble is what he calls "dark silicon."

It's a matter of simple math. From today's 45 nm node to the 11 nm technology of 2020, Muller said, we should be able to achieve a scaling factor of 16. Frequency won't grow as much as it has in the past, but an 11 nm design should run at 2.4X the speed of an equivalent 45 nm design. The power consumed per transistor will fall to perhaps 60 percent.

So, given the same power budget used for the 45 nm design today, if an 11 nm design has 16X the transistors running at 0.6X the power, "I can actually use only 10 percent of them in my new design," Muller said. "The rest is dark silicon. We need to find ways of lighting that silicon up."

Turning on the lights

So how to light things up? Muller started with three suggestions:

  • Push forward on new silicon technologies such as silicon-on-insulator (SOI), finding the optimal tradeoff between performance gains and power reduction. (Coincidentally, on March 23, IBM, ARM and Cadence announced a "Ready for SOI" program to develop an IP ecosystem for SOI).
  • Use energy-efficient, high-density memories to fill some of the "dark" space. Use power gating to turn them off when not needed.
  • Combine the best process technologies to fulfill various functions with 3D ICs, which will "become a critical part of how we deliver power-efficient solutions."

Muller also identified several areas in which further research and development is needed. These include stream programming for GPUs, programming solutions for manycore SoCs, design of energy-efficient on-chip interconnect, and "near and subthreshold circuits" that can use energy harvesting from heat and light already present in the environment.

Finally, Muller talked about Razor, a dynamic voltage scaling technique developed by ARM that can dynamically detect and correct timing errors. Razor tunes the supply voltage by monitoring the error rate during circuit operation, supposedly eliminating the need for voltage margins. Muller said Razor makes it possible to build a fault-tolerant processor that can recover from "fast moving and transient" timing errors.

It's the system, stupid

Muller concluded by noting something he learned in college - "it's the system, stupid." If you really want to save power, he said, you first have to think about where all the power goes. Muller noted that 300 million motors worldwide will represent 7 percent of global carbon emissions by 2020. Smart control can reduce motor power consumption by 25 to 40 percent.

"The important problem that faces all of us," Muller said, "is to optimize the real system, which is the world in which we live."

Conference co-chair John Donovan summarizes other parts of the virtual conference in a blog at the Low Power Design web site.

Richard Goering


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