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From: Andrei Alexandrescu (See Website For Email) (SeeWebsiteForEmail_at_[hidden])
Date: 2005-04-16 12:11:26

Peter Kümmel wrote:
> Moore`s law is about "Number of components per integrated function" or
> "Number of components per integrated circuit" (see original paper
> )
> The increasing of processor speed was only a "side effect".

That's true; I glossed over that detail. Nowadays we're not as good
anymore in increasing speed, while we stay reasonably strong at
increasing density. But the two are related: to make effective use of
more transistors you need to have data to keep them busy, so you need
speedy transportation of data around.

> Increasing the size of a circuit there is no physical limit which
> blocks Moore's law.

As the article says. Notice that wafer size, however, hasn't grown
exponentially during the years. Crystal defects are a killer.

> Here the theoretical upper limit of processor speed:
> 1. distance between to transistors: s = 10^-10 m (size of a atom)
> 2. Speed of light c = 3*10^8 m/s ~ 10^9 m/s (I'm interested in the upper
> limit)

Interesting approximation :o)

> travel time of a signal:
> t = s / c
> = 10^-10 m / (10^9 m/s)
> = 10^(-10-9) s
> = 10^-19 s
> Processor speed 1/t:
> 1/t = 10^19 Hz
> = 10^10 * 10^9 Hz
> = 10 billion GHz
> So there is much room to increase processor speed.

There are, of course, many fundamental (just as theoretical) issues that
this overly optimistic calculation neglects: crystal defects, thermal
effects, current density (already beyond nuclear reactor level in
today's processors), communication complexity, tunnel effects, quantum
effects... before long, orders of magnitude fall off rather quickly.


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