|Yeah we know what display you're talking about. The ones I've seen are LED--red numbers on a black background--but I suppose some could be LCD.|
What it displays depends on how the jumpers on the back of it are configured. And since you never get paperwork on what that configuration is, anytime you swap in a motherboard with different speeds you can only randomly experiment to see if you get it to show the right numbers. And then even if you get the turbo to show right you have to try again with the non-turbo speed. I don't recall ever getting both to show the right speed.
And I as mentioned before, the turbo pins could be jumpered so it's always turbo or there may be no turbo pins. In that case it could still show a speed there as the display is powered directly from the PSU.