Source : Free On-Line Dictionary of Computing

magic smoke
     
         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 {EPROM}s 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)