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.