Magic smoke (also factory smoke, blue smoke, or the genie) is a humorous name for the caustic

smoke Smoke is an aerosol (a suspension of airborne particulates and gases) emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwante ...

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, electric current, current, and frequency to power ...

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

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

in-joke An in-joke, also known as an inside joke or a private joke, is a joke with humour that 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 ...

that started among

electrical engineers Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in th ...

and

technician A technician is a worker in a field of technology who is proficient in the relevant skill and technique, with a relatively practical understanding of the theoretical principles. Specialisation The term technician covers many different special ...

s, which was later adopted by

programmers A programmer, computer programmer or coder is an author of computer source code someone with skill in computer programming. The professional titles ''software developer'' and ''software engineer'' are used for jobs that require a program ...

and

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

. 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 Computer Science and Artificial Intelligence Laboratory, MIT AI Lab ...

, a compendium of historical and current

hacker A hacker is a person skilled in information technology who achieves goals and solves problems by non-standard means. The term has become associated in popular culture with a security hackersomeone with knowledge of bug (computing), bugs or exp ...

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, a superseded scientific theory, postulated the existence of a fire-like element dubbed phlogiston () contained within combustible bodies and released during combustion. The name comes from the Ancient Greek (''burnin ...
hypothesis about combustion). Its existence is demonstrated by what happens when a chip burns up: the magic smoke gets out, whereupon the chip ceases to function, hence the smoke is essential for the chip's function.

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.

Post hoc ergo propter hoc ''Post hoc ergo propter hoc'' (Latin: 'after this, therefore because of this') is an informal fallacy that states "Since event Y ''followed'' event X, event Y must have been ''caused'' by event X." It is a fallacy in which an event is presumed to ...

the smoke (a sort of

élan vital ''Élan vital'' () is a term coined by French philosopher Henri Bergson in his 1907 book '' Creative Evolution'', in which he addresses the question of self-organisation and spontaneous morphogenesis of things in an increasingly complex manne ...

) is an essential part of the device and its operation via 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 when an expression that could offend or imply something unpleasant is replaced with one that is agreeable or inoffensive. Some euphemisms are intended to amuse, while others use bland, inoffensive terms for concepts that the u ...

s for the destruction of a component by overheating. When a device is powered on for the first time it is sometimes called a " smoke test", as any purely electrical defects would be revealed.

Red Hat Linux Red Hat Linux was a widely used commercial 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. Red Hat published the first non-beta release ...

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 primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...
* 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

{{Reflist

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 Computer Science and Artificial Intelligence Laboratory, MIT AI Lab ...

''Magic smoke''
entry at

FOLDOC The Free On-line Dictionary of Computing (FOLDOC) is an online, searchable, encyclopedic dictionary of computing subjects. History FOLDOC was founded in 1985 by Denis Howe and was hosted by Imperial College London. In May 2015, the site was up ...

Computer humour Electronics and society In-jokes Smoke