In general terms that's likely to be a CPU bottleneck, though other things can cause sub 100% utilization in games. You can try making sure V-sync or any other form of frame rate cap is off. I've also heard that sometimes it's driver related. However, because you are on Bulldozer I'd be fairly(not entirely) confident in it being a CPU bottleneck.
I checked out Max Payne benchmarks and it looked like for whatever loop was used that your CPU wouldn't cause problems. However, if your GPU use drops off in the swamps when your FPS does that's very likely your processor holding things up. When the processor really holds things up a more powerful GPU is held up waiting on the CPU so it's not particularly useful, though you can frequently have higher settings with the same FPS.
Far Cry 3 has a noticeable bottleneck(can result in less than 50fps) on the 4170 and that is clocked much higher than yours so I'm sure that you'll get higher settings and better FPS most of the time(as in better average FPS) with a 7950, but if your performance is like mine then driving will still slow you down.
As for Chivalry, I have no idea. There's probably a joke in there somewhere.