Magic smoke (also factory smoke, blue smoke, or the genie) is a humorous name for the caustic smoke produced by severe electrical over-stress of electronic circuits or components, causing overheating and an accompanying release of smoke. The smoke typically smells of burning plastic and other chemicals. The color of the smoke depends on which component is overheating, but it is commonly blue, grey, or white. Minor overstress eventually results in component failure, but without pyrotechnic display or release of smoke. A

power transistor A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics (for example in a switch-mode power supply). Such a device is also called a power device or, when used in an integrated circuit, a power IC ...

inside a

power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

is a frequent culprit for the acrid smoke. The name is a

running Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...

in-joke An in-joke, also known as an inside joke or a private joke, is a joke whose humour is understandable only to members of an ingroup; that is, people who are ''in'' a particular social group, occupation, or other community of shared interest. It i ...

that started among electrical engineers and technicians, which was later adopted by

programmers A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software. A programmer is someone who writes/creates ...

and

computer scientists Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (including th ...

. The

jargon file The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANET A ...

, a compendium of historical and current hacker jargon, defines:

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 The phlogiston theory is a superseded scientific theory that postulated the existence of a fire-like element called phlogiston () contained within combustible bodies and released during combustion. The name comes from the Ancient Greek (''burni ...
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.

The device operates as long as the magic smoke is trapped inside of it, but when the smoke escapes from it, the device ceases to operate. Ergo, the smoke is an essential part of the device and its operation, through undetermined ("magical") means.

Usage

This has led to phrases (and variants of) "You let the smoke out!", "The magic smoke is escaping." or "I think you set your power supply too high; there is magic smoke coming from that resistor!" as

euphemism A euphemism () is an innocuous word or expression used in place of one that is deemed offensive or suggests something unpleasant. Some euphemisms are intended to amuse, while others use bland, inoffensive terms for concepts that the user wishes ...

s for the destruction of a component by overheating. When a device is powered on for the first time, it is often called a " smoke test".

Red Hat Linux Red Hat Linux was a widely used Commercial software, commercial Open-source software, open-source Linux distribution created by Red Hat until its discontinuation in 2004. Early releases of Red Hat Linux were called Red Hat Commercial Linux. R ...

6.1 included the following text in the hardware compatibility guide:

Tier 3 Incompatible and Unsupported
CPUs A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
* Smokeless CPUs: Smokeless CPUs are incompatible with the linux kernel and it is doubted that any work will ever be performed to change this. They are simply too unreliable in even the most standard system configuration. Those with a CPU missing its Magic Smoke should switch to a new CPU.

The joke in the above quotation is the concept of a ''Smokeless CPU''—one in which the vital magic smoke has been released, rendering it inoperable. The joke remained in Red Hat 6.2, but was removed in a subsequent version.

References

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External links

''Magic smoke''
entry in the

Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANET A ...

''Magic smoke''
entry at FOLDOC Computer humor Electronics and society In-jokes Smoke