Speed, Heat, and Dark Silicon

We noted a few years ago that heat has become a limiting factor in processor speed. At the same time, we have been following the trend to use low-power chips originally designed for other applications in everything from more efficient supercomputers to lower power servers. Despite all this, the heat barrier continues to loom for ICT progress. 'Dark silicon' is its latest manifestation.

The New York Times reports,

…the most advanced microprocessor chips have so many transistors that it is impractical to supply power to all of them at the same time. So some of the transistors are left unpowered — or dark, in industry parlance — while the others are working. The phenomenon is known as dark silicon.

As early as next year, these advanced chips will need 21 percent of their transistors to go dark at any one time…And in just three more chip generations — a little more than a half-decade — the constraints will become even more severe. While there will be vastly more transistors on each chip, as many as half of them will have to be turned off to avoid overheating.

“I don’t think the chip would literally melt and run off of your circuit board as a liquid, though that would be dramatic,” Doug Burger, an author of the paper and a computer scientist at Microsoft Research, wrote in an e-mail. “But you’d start getting incorrect results and eventually components of the circuitry would fuse, rendering the chip inoperable.”

There are some potential solutions. For example, "Intel recently developed a way to vary the power consumed by different parts of a processor, making it possible to have both slower, lower-power transistors as well as faster-switching ones that consume more power. "

The article is based on the paper "Dark Silicon and the End of Multicore Scaling".