I recently purchased a new ASUS laptop with an i5 460m in it. Thus far I have never ever seen it clock itself to the rated 2.53GHz (not to mention turbo boost). It has always hovered at around 1200MHz. I watched the clock speed using CPUZ and even running 4 threads of Prime95 did not entice it to up its clock speed.
As far as I understand two things should be happening:
1) Intel speed step should bump the processor to its rated 2.53GHz when its under a heavy load
2) Turbo boost should kick in if the load is sufficiently high and bump it a little higher
Two things that I could envision messing with this are the ASUS Super Hybrid Engine and the ASUS Power4Gear utility that I have installed.
Connect the laptop to AC power and then try.Also change win7 powerplan to balanced or high performance.Turbo boost kicks in when app you are using is single or double threaded.It also depends upon the temp of your cpu.