magic smoke

magic smoke
 n.

   A substance trapped inside IC packages that enables them to function
   (also called blue smoke; this is similar to the archaic phlogiston
   hypothesis about combustion). Its existence is demonstrated by what
   happens when a chip burns up -- the magic smoke gets let out, so it
   doesn't work any more. See {smoke test}, {let the smoke out}.

   Usenetter Jay Maynard tells the following story: "Once, while hacking
   on a dedicated Z80 system, I was testing code by blowing EPROMs and
   plugging them in the system, then seeing what happened. One time, I
   plugged one in backwards. I only discovered that after I realized that
   Intel didn't put power-on lights under the quartz windows on the tops
   of their EPROMs -- the die was glowing white-hot. Amazingly, the EPROM
   worked fine after I erased it, filled it full of zeros, then erased it
   again. For all I know, it's still in service. Of course, this is
   because the magic smoke didn't get let out." Compare the original
   phrasing of {Murphy's Law}.
    

magic smoke

   <electronics, humour> A substance trapped inside {integrated
   circuit} packages that enables them to function (also called
   "blue smoke"; this is similar to the archaic "phlogiston"
   hypothesis about combustion).  Its existence is demonstrated
   by what happens when a chip burns up - the magic smoke gets
   let out, so it doesn't work any more.

   See {Electing a Pope}, {smoke test}.

   {Usenet}ter Jay Maynard tells the following story:

   "Once, while hacking on a dedicated {Zilog Z80} system, I was
   testing code by blowing {EPROMs} and plugging them in the
   system, then seeing what happened.  One time, I plugged one in
   backward.  I only discovered that *after* I realised that
   {Intel} didn't put power-on lights under the quartz windows on
   the tops of their EPROMs - the die was glowing white-hot.
   Amazingly, the EPROM worked fine after I erased it, filled it
   full of zeros, then erased it again.  For all I know, it's
   still in service.  Of course, this is because the magic smoke
   didn't get let out."

   Compare the original phrasing of {Murphy's Law}.

   [{Jargon File}]

   (1995-01-25)