Well, do you get around 30fps constantly or would it go to 60fps then flicker down to 15fps every couple of minutes?. If you do get the fps drops, there's many different reasons.
- Problem with your motherboard. If you've gotten a motherboard with a phase of 4 + 1, this may have a problem with running your Octocore CPU (8320), Also if you do have a 4 + 1 phase motherboard, try and turn off any power-consumption options in your bios (Press Del on startup, mainly). Most motherboards would give less power to your CPU depending on your load or will have a 'green' feature, which would then draw less power to your CPU. If you were to pick a motherboard that supports an octo-core CPU, I'd suggest any motherboard with the correct watt (I believe 125w, is for your FX-8320 Black Edition). I personally use gigabyte boards.
- Another problem could be your cooling, if your CPU hits high temperatures that means there's either
- A lack of thermal compound
- You've got a cheap heat-sink
What this would do is make your CPU throttle, this basically down-grades your CPU's multiplier from around x14 to around x2, making the 3.6GHz to around 1GHz, causing the horrendous CPU FPS drops in games. (I used to have the same problem). Just make sure you check your temperatures.
All of this is probably, a worst case scenario. I used to have a motherboard (MSI-GM) that supported a 95w CPU, when my CPU was 125w. Also, does this happen in other games?
I believe the 'APM' Feature on the BIOS, as well as AMD ' Cool 'n' Quiet' feature, about 99% of motherboards come with this horrible, power-saving feature, just turn it off. Anyways, I use a gigabyte motherboard, this is why I use 'Del' to access the bios.
EDIT: Having an 8 + 2 power phase, would also allow for better over-clocking, turning your 8320 to basically a 8350 if you overclock it to 4GHz. Placing your motherboard, would also help.