Does Dennard scaling predict a power wall How does Dennard p

Does Dennard scaling predict a power wall? How does Dennard predict the heat flux will scale with techology generations?

Solution

Dennard scaling – This suggests that power requirements are proportional to area (both voltage and current being proportional to length) for transistors. Combined with Moore\'s law, performance per watt would grow at roughly the same rate as transistor density, doubling every 1–2 years.

According to Dennard scaling transistor dimensions are scaled by 30% every technology generations, thus reducing their area by 50%. This reduces the delay by 30% and therefore increases operating frequency by about 40% . Finally, to keep electric field constant, voltage is reduced by 30%, reducing energy by 65% and power by 50%.Therefore, in every technology generation transistor density doubles, circuit becomes 40% faster, while power consumption stays the same.

The exponential processor transistor growth predicted by Moore does not always translate into exponentially greater practical CPU performance. Since around 2005–2007, Dennard scaling appears to have broken down, so even though Moore\'s law continued for several years after that, it has not yielded dividends in improved performance.The primary reason cited for the breakdown is that at small sizes, current leakage poses greater challenges, and also causes the chip to heat up, which creates a threat ofthermal runaway and therefore, further increases energy costs.

The breakdown of Dennard scaling prompted a switch among some chip manufacturers to a greater focus on multicore processors, but the gains offered by switching to more cores are lower than the gains that would be achieved had Dennard scaling continued.In another departure from Dennard scaling, Intel microprocessors adopted a non-planar tri-gate FinFET at 22 nm in 2012 that is faster and consumes less power than a conventional planar transistor.