I just got  a brand new E6540 as my corporate laptop. Due to a mistake in our IT department mine came with the 65watt power adapter. With that connected I get this:

Note the meagre 798mhz core speed.

Now I've just connected it to a colleague's 130 watt adapter and ever since when I disconnected my Dell from the 65 watt adapter I suddenly get this:

So... when my laptop is running on battery power it's suddenly significantly faster than when it's on AC.

Any ideas?