Why CPUs are unpredictable - chaos

[Silicon Skum]

You might think the the CPUs and ICs that drive the computer world are good models of deterministic precision........Guess again!

Their behaviour is inherently unpredictable and chaotic. Intel's Pentium 4 CPU core has 42 Million transistors and the newer Itanium 2 has no less than 410 million of them!.
Hugues Berry of the National Reasearch Institute for Information and Automation based in France, says "Their performance can be highly variable and difficult to predict" The team from the research institute ran a standard program repeatedly on a simulator which engineers use to test microprocessors, they found that the time it took to complete the task varied greatly from one run to the next.

Within the irregularity, the team discovered a pattern, that of the mathematical signature of "deterministic chaos", a property that governs other chaotic systems, such as the weather.
Such systems are extremely sensitive to small changes, a change at one point can lead to much wider fluctuations at a later time. For the microprocessor, this means that the precise course of a computation and the length of time taken, is sensitive to the processor's state when the computation began.

Here is the website for the research paper: (warning, heavy reading)

http://arxiv.org/abs/nlin.AO/0506030

So now you know why it feels like doing a repetative task on a computer can sometimes feel longer than other times - it prolly IS.

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my sig disappeared from the image host (?)
But at least I have a Josh Award!

[Google]

[ToggleHead]

good read...very cool......
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[Xal]

Great find SS
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