hello.
Its call lightspeed and it works on the T3, not sure if it works on teh T5 though.
You can probably go to palmone under software and type light speed and you should get the info. its not free, but you can test it for a couple of days before you have to buy it.
Good luck.
Messing with any overclocking (underclocking) software can royally mess up your machine. I DO NOT SUGGEST IT. To be perfectly honest the T5 is fast enough. I wouldn't run the risk of frying the poor thing just to mess around with the speed.
That's my 2 cents. Best of luck to you if you try it. Let us know if it works.