Turbo button refers to a button on a piece of electronic equipment, which makes the equipment run faster (or slower) in some way. Its three most popular incarnations are:
Case buttons including turbo buttonOn personal 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. Systems could also use the keyboard combination of ctrl-alt-+/-, '-' switching turbo OFF and '+' switching it ON (ctrl-alt-\ to toggle between turbo/normal mode on ITT Xtra machines). 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". The turbo button was often linked to a MHz LED display on the system case, or to a "hi"/"lo" LED display. Today, the functionality offered by the turbo button is considered to be obsolete[dubious – discuss] and has thus disappeared from modern computer models. Modern PCs only have software replacements[1] for full turbo button functionality. Some modern PCs that support ACPI power management allow the user to switch a PC's performance state between low- and high- performance modes, however the feature is rarely bound to an external button.
On computer keyboards, the Turbo button may affect the computer's speed (as stated above) or adjust the keyboard repeating rate[2]
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, labeled "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). An enhanced or upgraded controller's "Turbo" function 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).
