After extensive research with the Turbo buttons I had I came to the conclusion that it was only there to help you spend your money quicker...
That and acutally lose performance on the PC:

http://www.pcguide.com/ref/case/switchTurbo-c.html

But my IT manager at the time was delusional back then (or put in too many hours) and would put on goggles and driving gloves , hit the turbo button and thought he was going to light or "ridiculous" speed or time travel - ya know, cuz the machine was going sooo fast!... yeah... I told him it was to start the time machine and it was just disguised as a turbo button.

So do i, if you miss the highpitched noise they used to make when dialling in then check out This site.
Woo-hoo! Woo-hoo! Woo-hoo! Man I missed that, now I'm good for another 5 years.