Yes it is possible. It is called IDA (Intel Dynamic Acceleration Technology) It was introduced on C2 Mobile Dual Cores. What it does is when one core is not being used (C3 state, I could be wrong on that technical part) the core in use can increase it's multiplier. This can for example help give a boost when running a single threaded application. It is kind of the forerunner of the Turbo Boost on the i7's you might of read about.
OK so we know why this can happen and I have on very rare occasion seen my T9400 do. But I am concerned if this is for more than just a brief period are your cores functioning properly? I ask because it seems to me with any current usage of say, online, multiple browser windows open and a few other apps open, how can one of your cores be in a C3 sleep state? OK maybe if you where trying to not run anything but still.
That is the why but I would rather have 2 Cores at 2Ghz vs 1 Core at 2.2Ghz? Open up a bunch of apps and see if the multiplier goes to 10x as it should. If it does all is fine if not post back as that is not good.