One of my machines has a "Turbo" button that changes from "HI" to
"LO".
It does make a noticeable difference in speed. Probably inserts a
bunch of NOPs in or something. Comes in handy when I'm trying to play
older games.
On older machines it did actually change the clock speed.
Gordon.
Yes, done with two ways in hardware: Oscillator output or crystal
divide by n usually found on decent boards or select either high or
low frequency oscillators or crystals (on cheapo boards).
Cheers, Wizard