Yes, our first family PC was a 386 that we could slow down from 33 to 16 MHz with the Turbo button. It even had the segment display to show the current clock rate.

I knew what it was for and had some old games that ran too fast, but from what I remember, in most cases 16 MHz was still much too fast, so I didn't use the button much.

I think it was no problem to switch Turbo mode on and off in the middle of running software.