資料來源 : pyDict

宇宙射線

資料來源 : Free On-Line Dictionary of Computing

cosmic rays
     
        Notionally, the cause of {bit rot}.  However, this is a
        semi-independent usage that may be invoked as a humorous way
        to {handwave} away any minor {randomness} that doesn't seem
        worth the bother of investigating.  "Hey, Eric - I just got
        a burst of garbage on my {tube}, where did that come from?"
        "Cosmic rays, I guess."  Compare {sunspots}, {phase of the
        moon}.  The British seem to prefer the usage "cosmic showers";
        "alpha particles" is also heard, because stray alpha particles
        passing through a memory chip can cause single bit errors
        (this becomes increasingly more likely as memory sizes and
        densities increase).
     
        Factual note: Alpha particles cause bit rot, cosmic rays do
        not (except occasionally in spaceborne computers).  Intel
        could not explain random bit drops in their early chips, and
        one hypothesis was cosmic rays.  So they created the World's
        Largest Lead Safe, using 25 tons of the stuff, and used two
        identical boards for testing.  One was placed in the safe, one
        outside.  The hypothesis was that if cosmic rays were causing
        the bit drops, they should see a statistically significant
        difference between the error rates on the two boards.  They
        did not observe such a difference.  Further investigation
        demonstrated conclusively that the bit drops were due to alpha
        particle emissions from thorium (and to a much lesser degree
        uranium) in the encapsulation material.  Since it is
        impossible to eliminate these radioactives (they are uniformly
        distributed through the earth's crust, with the statistically
        insignificant exception of uranium lodes) it became obvious
        that one has to design memories to withstand these hits.
     
        [{Jargon File}]