AFAIK no first-party IBM PC ever had a turbo button, only clones, and my only personal recollection of pre-286 clones running significantly faster than 4.77 MHz were the Compaq Deskpro and AT&T PC 6300.

I don't know about the PC 6300 — I only ever used it to run Aldus PageMaker, which, running under Windows on an 8086, could use all the speed it could get — but the Deskpro had a keystroke combination to switch between native and compatible speeds rather than a button.