Intel's research labs have prototyped a resilient microprocessor that delivers as much as 41% more throughput using the same amount of energy as a comparable conventional core.
If applied to commercial processors, this resilient/adaptive design would, under ideal conditions, deliver better than guaranteed throughput, says Keith Bowman, a researcher at Intel's Circuit Research Laboratories. “It would result in higher performance from a chip rated for a lower performance,” Bowman says.Under less than ideal conditions – marked by power dips, temperature changes and aging transistors – this miserly design would optimize performance and deliver guaranteed throughput more efficiently than would cores that adhere to conventional architectures.
This self-tuning by means of built-in error detection and correction eats up cycles but not as many as would be eaten up by the conventional method that relies on cycle-wasting buffers called guardbands. The net result is more efficient processing. “We think it's a great tradeoff,” Bowman says.Intel researchers are now developing prototypes that expand the scale of the error detection and correction, and are determining what kind of impact these adaptive cores would have on commercial processors that might someday use them, he says. While promising, the technology is not yet on the formal path to being incorporated in commercial products, he says.
Today's microprocessor cores are designed to perform at guaranteed levels regardless of fluctuations in temperature and voltage that they might face. They are also designed to hit those performance levels over a specified lifecycle by taking into account the expected material degradation that takes place over time, Bowman says.
To meet these performance guarantees chip makers build in guardbands that provide reserve cycles that ensure the delivery of specified throughput even in worst case scenarios where voltage, temperature and aging parameters actually do hurt performance. As a result, conventional processors use more power for lower throughput than they would without guardbands, he says.
The Intel prototype core includes adaptive circuits that eliminate guardbands. Instead, these circuits detect errors caused by the voltage, temperature and aging factors and correct for them on the fly without requiring reserve cycles. That results in either maximized throughput or minimized energy requirements that in either case outstrip performance of conventional processors, he says.
These adaptive circuits do expend resources, but less than would be tied up with guardbands because variations that affect performance are relatively infrequent. Over time it is more efficient to spend the cycles as needed than to keep guardbands all the time.