Maximum PC

A little over two weeks ago, I started reviewing a game that runs off of the ArmA II engine called Iron Front: Liberation 1944. However, the problem that rose up was that I could barley run the ArmA II engine. I can get an average of 45-60 FPS with lowest settings for ArmA II while for Iron Front: Liberation 1944 I can only get about an average of somewhere between 20-45 FPS on average with the lowest settings. After doing some research and learning that the ArmA II engine is a very CPU-heavy engine, I decided that I would upgrade my CPU from the 2.7 triple-core I had originally put into my machine. However, I'm unsure of what AMD CPU would be ideal for the ArmA II engine and I am hoping that I can get some help from this forum. My current specs are listed below and I'm currently looking the six-core AMD Phenom II X6 1045T 2.7 GHz. It's compatible with my machine, but I'm unsure if it's what a computer expert would call "Ideal" for the ArmA II engine.

SPECS:
Processor: AMD Phenom II X3 720 2.8GHz
Motherboard: GIGABYTE GA-MA790GPT-UD3H AM3
Graphics Card: SAPPHIRE 100283L Radeon HD 5770 (Juniper XT) 1GB 128-bit GDDR5
RAM: Kingston ValueRAM 4GB (2 x 2GB)
Hard Drive: WD Caviar Blue WD3200AAKS 320GB 7200 RPM
Power Supply: CORSAIR CMPSU-450VX 450W ATX12V

Short of getting something new, yes, that will probably do a lot better in ARMA II. Although "ideally" would be the best processor for AMD, an AMD FX-8150

So I got the CPU last Friday and I just today tried putting the thing into my motherboard. It fit, but there's a slight problem; the computer will not boot up beyond the motherboard start-up screen. For some strange reason I can still get to the boot screen (the "Select Where To First Boot From" screen) but nowhere else. Letting the computer do its own thing or trying to get to the BIOS will either crash or freeze the computer.

I suspect that my problem might be because I had originally set my motherboard to overclock my slower, 3-core CPU and inserting the new 6-core CPU with the default fan might not be enough to keep the CPU cool enough to operate. However, with a little help from someone else I was able to remove the CMOS battery from the motherboard and place it back in after about two minute (I was under the impression that removing the CMOS battery for a few minutes would set the BIOS back to the defaults). Also, since I wrongly installed the 3-core CPU I cannot put it back into the motherboard.

I currently have no idea what I should do if I did anything wrong and I would really appreciate any help I can get.