Over at IEEE Spectrum, Rachel Courtland writes that after decades of fulfilling Gordon Moore’s prophesy of steadily doubling transistor densities every 18 to 24 months, the end may be in sight.
The sheer density and power levels on a state-of-the-art chip have forced designers to compensate by adding error-correction circuitry, redundancy, read- and write-boosting circuitry for failing static RAM cells, circuits to track and adapt to performance variations, and complicated memory hierarchies to handle multicore architectures. The problem, Kahng says, is that “all of those extra circuits add area.” His group has been scouring company specs and deconstructing images of chips for years, and they’ve come to an unsettling conclusion: When you factor those circuits in, chips are no longer twice as dense from generation to generation. In fact, Kahng’s analysis suggests, the density improvement over the past three generations, from 2007 on, has been closer to 1.6 than 2. This smaller density benefit means costlier chips, and it also has an impact on performance because signals must be driven over longer distances. The shortfall is consistent enough, Kahng says, that it could be considered its own law.
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