The turbo button originates from Taiwanese "Turbo XT" clones that would run an 8088 or V20 at 8, 10, 12 or even 16 MHz with turbo engaged and 4.77 with it off.
Later 386 and 486 systems implemented turbo logic in different ways. Some by reducing bus speed, some by disabling CPU caches, some by inserting wait states for memory access.
Later 386 and 486 systems implemented turbo logic in different ways. Some by reducing bus speed, some by disabling CPU caches, some by inserting wait states for memory access.