Most games don't utilize multiple cores well or at all, even though BF3 does to some extend, you still have a CPU that is meant to be used for serving multiple threads at once. You need stronger processing power per core, not a lot of cores. It's simply the internal architecture of your CPU(s) that is limiting your system.
BF3 supports up to 4 cores, afaik, quite well. In fact it's preferred to have 4 cores for it. That's very good multicore support considering majority of the games today struggle to use 2 cores efficiently.
so no, there's no patch for multi-cpu support
the fix is to get a standard performance CPU rather than server CPU. The architecture is just not the same