Turbo button

Turbo button generally refers to a button (control) on a piece of electonic equipment, which makes the equipment run faster in some way. Its two most popular incarnations are:

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• On some desktop computers, the Turbo button changes the effective speed of the system. It usually accomplishes this by either adjusting the CPU clock speed directly, or by turning off the processor's cache, forcing it to wait on slow main memory every time. The button was generally present on older systems, and was designed to allow the user to play older games that depended on processor speed for their timing. Of course, calling it a "turbo" button when its function slows the system down can be a bit misleading, but the button was usually set up so the system would be at full speed when the button was "on".
• On some video game controllers, a Turbo button or Autofire (sometimes implemented as a sliding switch instead of a button) determines the repeat rate of another action button. For example, the Nintendo Entertainment System's controller has two action buttons, labelled "A" and "B". Normally, pressing the "A" button will result in the action associated with "A" being done once -- for example, a character will jump once. This happens even when the "A" button is "held down" (depressed continually). A controller's "Turbo" functon will change this held-down functionality, so that the character would jump repeatedly, as if the "A" button were being pressed many times very quickly (a desirable feature in games where, for example, the "A" button fires a projectile).