Turbo button

When pressed, the "turbo" button is intended to let a computer run at the highest speed for which it had been designed.

[4] Disengaging turbo mode slows the system down to a state compatible with original 8086/8088 chips.

The turbo button could be linked to a turbo LED or two-digit segmented display on the system case, although in some cases, the indicated frequency (in MHz) was not a measure of the actual processor clocks, but the two "fast" and "slow" display options set by jumpers on the motherboard.

As software began to rely on other timing methods, the turbo feature became mostly irrelevant to new programs.

[10][11] This caused a lot of confusion and misunderstanding about the purpose and naming of the button in retro computer forums and communities[citation needed].

If the turbo LED is on, that always means the CPU is running at full speed, regardless of how the switch is wired.

Case buttons including turbo button
The LED display showing the CPU clock frequency, in MHz , of an Intel 80486 based computer. The turbo button is the small button below the segment display; the amber light above is a secondary indicator of the turbo button state.