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In a sense it has already happened. The clock speeds in production chips have not increased markedly in the last 10 or so years. Take a program that has lot of

In a sense it has already happened. The clock speeds in production chips have not increased markedly in the last 10 or so years. Take a program that has lot of unpredictable branching, random memory accesses and heavily interdependent calculation (the next command always depends on the previous one) and you are not really much faster than old CPU's. The speedups in single core performance in recent years have mostly come from increasing bandwidth, automatically taking advantage of some concurrency (Out of order execution), more and more SIMD instructions etc etc. Interestingly enough if you want to write very high performance CPU code it's almost like writing OpenCL for GPU execution. I'd go so far to even claim that right now the best way to write high performance CPU code is to use Intel's OpenCL implementation for their CPU.

mikeash 13y ago
Moore's Law was never about clock speeds. It was always about feature size i.e. number of transistors per square inch. For a long time, transistor count directly enabled higher clock speeds, and so people conflated the two. But the original statement of the Law has no mention of clock speeds. Why does it matter why single-core performance has continued to improve? It used to be clock speed, now it's something else, but it's still getting better all the time.