May 15, 2003

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.

Posted by Jargon File at May 15, 2003 10:39 AM

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