magic smoke

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magic smoke

(electronics, humour)
A substance trapped inside integrated circuit 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 Electing a Pope, smoke test.

Usenetter Jay Maynard tells the following story:

"Once, while hacking on a dedicated Zilog 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 backward. I only discovered that *after* I realised 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.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in classic literature ?
At lengthened intervals a log cabin, with its little space of cleared land about it, nestles under a rising ground, and sends its thread of blue smoke curling up into the sky.
"It is well," said Mohammed Beyd, blowing a little puff of blue smoke straight out before him.
Morison selected a cigarette from his crested case, lighted it, blew a thin line of blue smoke toward the moon, and smiled.
The Prince, as he lounged in his wicker chair and watched the blue smoke of his cigarette curl upwards, looked more like an Italian--perhaps a Spaniard.
Fentolin had lit a cigarette and was watching the blue smoke curl upwards to the ceiling.
On the hill-top above me sat the rising moon; pale yet as a cloud, but brightening momentarily, she looked over Hay, which, half lost in trees, sent up a blue smoke from its few chimneys: it was yet a mile distant, but in the absolute hush I could hear plainly its thin murmurs of life.
Jets from the Royal Air Force Aerobatic Team, as they are officially called, painted the Big Apple's skies with signature red, white and blue smoke trails during the flypast.
Fire begins to engulf the vehicle, turning the gauzy plumes of bright blue smoke into a more ominous black.
As CEO of Union Square Hospitality Group (USHG) Meyer continues to own and operate a slew of successful eateries, including Gramercy Tavern, Blue Smoke and Jazz Standard as well as a catering division that operates concessions at major sports facilities including Citi Field and Saratoga Race Course.
You can treat your taste buds to one of the resort's restaurant concepts, Blue Smoke on the Bay, where all local produce is cooked over a wood fire, the only one you will find in the Lake District.
WE'VE all heard mopeds with two-stroke engines buzzing around the streets in a haze of oily blue smoke, like angry wasps with their backsides on fire.
When the hard hats and hammers are laid down, Low Wood will offer new leisure and spa facilities, a modern atrium area and a new restaurant, Blue Smoke, while guests will have 131 rooms to choose from, including a host of high-end suites.