here is a really good read about Dual-Core and SMP, very understandable. see below
And if I get it right, gaming does not gain all that much, its more for multi tasking,,,,
Do dual-core and SMP double the speed?
No. If you have two 2.4 GHz cores or processors, you do not have a 4.8 GHz computer. You have a computer that can process two threads at a time at 2.4 GHz each. This will benefit applications (such as Adobe Photoshop and Premiere) that are multithreaded, and it will allow you to run two processor intensive programs at once without lag. That leads me to the next point…
Will dual-core or SMP chips make my games run faster?
No. Games are single-threaded, so they’ll only use one of the cores. However, if you are, for example, gaming and ripping MP3s at the same time, it will mean your game won’t lag. So if you’re going to be using a computer mostly for gaming, get a faster single-core chip over a dual-core one
Battlefield 2142...I guess thats ovious since its basicly a mod of BF2 XD. On my G15, I've watched my CPU usage, and it bounces from 60-70% usage, I have hyperthreading, so anything over 50% is using both threads. Most games dont do this and there isn't an application running in the background using the CPU to that extent.