Older turbokey versions worked when you pushed the power button.
Turbokey on the M4A89GTD Pro/USB3 is actually a switch on the board, you can see a pic here (2nd pic from the top)-
As for how it works, never looked into turbokey that hard. Like all automatic overclocking tools, its never going to give the results that manual overclocking does. This sort of result is fairly common with all the automatic overclocking tools I've ever seen-
Turbo Key II:
Turbo Key II is a hardware utility that is controlled by flipping a switch, allowing you to overclock your system. There is no input or changes made from the user, it is all automatic. When I flipped the switch, it overclocked the Phenom II X4 965 processor to 3.70GHz (217.7 x 17), but it sacrificed the memory speed and latencies dropping them to 870MHz with timings of 8-8-8-20. With the overclock and the reduction of the memory, I ran PCMark Vantage to see how it faired and ended up with a score of 4954, which a bit lower then the stock score of 5127 so the auto clock actually hurt the performance.
IMO if you want to overclock, do it manually from the BIOS.