The Turbo button was a button found on earlier (386 and 486) PC computers that would increase or decrease the performance of the computer. This button was needed for backwards compatibility in older programs and games that were written for a specific speed of computer. When faster computers were released, because the programs were written for a slower speed of computer, it would cause the program to run extremely fast, often making them unusable. Using the turbo button, the user could slow the computer down allowing them to use these programs. The picture shows an example of the Turbo button.
Also see: Button