Why CPUs aren't getting any faster (2010)

Re:Why CPUs aren't getting any faster (2010) by michael_nielsen on Monday April 28, 2014 @03:00PM (#7662130)

It means signals can only propagate about 6 centimeters during a single CPU clock cycle. That makes accessing information off-chip difficult in a single cycle, since 6 centimeters is on the same order as the linear scale of most motherboards.

This limit doesn't immediately impact computations that are carried out entirely on-chip. I expect that's the great majority of computations on today's CPUs, which typically have large caches. So I'm not sure the GP's explanation is correct, although it's certainly interesting.

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Re:Why CPUs aren't getting any faster (2010) by lotsofmangos on Monday April 28, 2014 @05:11PM (#7663103)

As an explanation for why you cant get clock speed increases of the same order of magnitude as you could previously, without changing the entire technology, it would seem correct.

6cm now means that you only need to double twice to get to less than the die width.

Also, electricity does not propagate through copper at c, but at between 40% and 90% of it, depending on the inductance and capacitance of the circuit, so you are looking at even less of an increase before you start running into some really thorny problems as not only are you running up against relativistic limitations, but different bits of your chip can be doing it at noticeably different times.

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