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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.