Magic smoke

Smoke released from an electronic component

An integrated circuit rendered useless after overheating.

Magic smoke (also called factory smoke or blue smoke) is smoke produced by malfunctioning electronic circuits. The origins of the magic smoke have become a running in-joke that started among electrical engineers and technicians before it was more recently adopted by computer programmers. The actual origin of blue smoke is the black plastic epoxy material that is used to package most common semiconductor devices such as transistors and integrated circuits, which produces a bluish coloured smoke during combustion. Smoke from other components that do not use this epoxy may vary in colour, but still be identified as the same phenomenon for purposes of the joke.

Joke

Smoke is frequently observed to come out of electronic components when overheated, often through exposure to an extreme electrical current usually caused by a low-resistance failure or the application of excess voltage through some cascading failure of the circuit. According to the joke, manufacturers put a portion of magic smoke into every electronic component, and the device functions normally so long as the smoke does not escape. Once the magic smoke has been released, the device lacks one or more key components and no longer functions correctly. The smoke thus can be thought of as an essential part in the device's function. It is also noted that once let out, the magic smoke cannot be put back in. The joke deliberately uses common logical fallacies to humorously characterize the causes and effects of electronic device failure.

Power plants produce the smoke and send it to their customers through a grid of power lines. If they produce more smoke than the customers can use, the excess smoke goes out the stack.

In some variations of the joke, it is alleged that the major microchip production companies (especially the large microprocessor manufacturers) are involved in a conspiracy to keep the true nature of their products under wraps.^[1]

Usage

This has led to use of the phrases (and variants of) "leaking smoke", "the magic smoke is escaping", or "you let the smoke out!" as a euphemism for the destruction of a processor, integrated circuit or other electronic component, by overheating.

When a device is powered on for the first time, it is often called a "smoke test".

See also

• Phlogiston theory

References

1. ^ John R. Barnes (2004), Robust Electronic Design Reference Book, Springer, ISBN 9781402077388, http://books.google.com/?id=V2GIeUAZj0kC&pg=PT308&dq=%22Magic+smoke%22 

External links

• Magic smoke entry in the Jargon File
• Magic smoke entry at FOLDOC
• Lucas Replacement Wiring Harness Smoke (for automotive electrics)
• "Magic Blue Smoke Refilling Kit" Magic Smoke Refill kit from Sparkfun