Quote Originally Posted by Daevyll View Post
That would be prefectly true if the game was the only thing running on your PC.
However, that's never the case, any PC will have a multitude of other processes running. And so long as there is any software running that does make full use of the quadcore (such as the OS if you have Vista 64 for example) it does help you out indirectly by making other things more efficiently thus freeing up resources for the game.
There are two catch 22's here:
(a) Excepting a few really pricey, high end Quadcores... the Q series aren't _proper_ Quad *cores*. What they are amounts to 2 dual cores welded to make a single processor. In effect this means more cache, less clocking speed (thus slower cache), and only up to 2 concurrent threads. The point is that at any given instruction only two threads have a core, the other two are iddle. The reason is that both cores share the same connection (path) with the cache and RAM:

Now if both dual-cores have continuous 'load' that won't matter as much (because you will have good caching results) but if one core 'suddenly' has to step in for a certain process caching will be much poorer: indeed there will be quite a bit of non-cached instructions as a new program stack needs to be loaded into the registers and the old one needs to be written to RAM! So if you have the choice between a faster dual core with comparatively (per-core) large amounts of cache versus a Quadcore with lesser per-core performance you can expect the Dual Core to outperform the Quadcore in most situations. (Heavy media encoding and decoding is the notable exception.)
(b) Proper process scheduling assings some kind of priority to certain processes over others. That is, the Game is given max time slices to execut its code for better responsiveness; other processes are kept in the background as much as possible. It also means that there will be very little going on apart from your game: for instance your desktop will not be refreshed if you play in full screen modus, because the OS knows that the entire desktop is pretty much idle anyways and thus it defers desktop refreshing till later. That is also why windowed mode incurs heavier workloads for your system when running a game: there *are* notable background processes going on.