Your GPU might be bottlenecking, though i'm not sure since Sandstorm is quite CPU-intensive, too. But this might be one explanation of low CPU usage. Lower your graphics settings to find out.
Your CPU is not actually at 50%. The far more likely situation is a few cores (2-4 is my guess) at almost full usage, while the rest stays at a far lower usage. Windows often combines this load and doesn't show the actual usage. So while it might show 50%, having just one core that is used to capacity actually means the CPU is at its limit.
I still have an i5 2500k (oc), and usage is quite high ingame. The additional threads your CPU has might explain the lower usage (windows combine usage) and might also say something about the number of cores actually used (my guess would also be "around 4"). Additionally i'd suggest a 6- to 8-core CPU for best experience (in case you're thinking about upgrading), but it should not be one with a lower frequency.
I've researched a bit more about how to find a CPU limit. It appears that in most cases, if the GPU is not used to capacity then the CPU is limiting, even if logging software like MSI's Afterburner does not show it (because when multicore CPU's came out Windows started shifting Threads around all the time in order to make multithreaded workloads possible, hence the more cores the more difficult it becomes to spot a CPU limit). So those screenshots clearly show a CPU limit except the main menu shot (main menu limits fps automatically =60fps).
There are two ways to verify the CPU limit:
- downclock the CPU again (or deactivate a core) and benchmark again under the same circumstances -> FPS should go down, too.
- Increase resolution of the game (you can use the Super Sampling setting in Sandstorm) to see if GPU usage increases without noticably influencing FPS (ordinarily, in a GPU limit this would result in lower FPS).
Do EITHER of those, not both together, and don't touch other settings while you try one method. And don't use the main menu as reference ;).
ok for the tips, but I will upgrade my GPU very soon. I finally found a balance between stability & quality.
I've limited my frame to 90fps, FXAA ON, VsyncOFF , tweaked a bit in nvidia pannel.
Added those lines in Engine.ini
This is much better, more consistent frames & look good