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.

