= M =
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.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.