The End of Moore’s Law

I was reading “The Problem with Threads” by Prof. Ed Lee, and noticed the following claim right on the first page:

Many technologists predict that the end of Moore’s Law will be answered with increasingly parallel computer architectures (multicore or chip [multiprocessors], CMPs)[15].

This quote confuses me, because, to the best of my knowledge, Moore’s Law has not ended, and the industry’s move to multicore/manycore processors is not directly related to the imminent demise of Moore’s Law. Moore’s Law is the claim that transistor density in integrated circuits approximately doubles every two years. As far as I know, that remains basically true for the time being, and current speculation is that it will continue to hold for at least 10 years.

What is driving the move to multicore designs is that we can no longer effectively use those extra transistors to increase the speed of a single sequential instruction stream. Ramping up clock speed increases heat dissipation, and doesn’t improve performance very much if memory latency doesn’t significantly change. Techniques like caching, pipelining, and superscalar execution help, but only to an extent. Hence the move to multicore designs and chip-level parallelism.

That said, I’m definitely not a hardware guy, and doubtless Prof. Lee has forgotten more about processor design than I am ever likely to know. And when Moore’s Law ends, that may well encourage the multicore trend even more—but my understanding is that the eventual demise of Moore’s Law and the current move to multicore architectures are not directly related. I’m curious to know if I’m mistaken.

(As an aside, text quoted above cites “Multicore CPUs for the Masses” in ACM Queue as support for the claim that the industry is moving toward multicore designs. While that is true, the article makes no mention of Moore’s Law.)


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