cosmic rays

2 definitions found

cosmic rays - Free On-line Dictionary of Computing (26 May 2007) :

  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]
  

cosmic rays - Jargon File (4.4.4, 14 Aug 2003) :

  cosmic rays
   n.
  
     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.