I just did a little funny experiment in the game/sim "Train Simulator 2013". I normally have good FPS in it (around 30) at full settings.
What I did was make a really, really long train so that the calculations the sim needed to make were enormous (the sim is quite realistic, it takes all things into account like speed/acceleration, G-forces, comfort levels, possible wheel slip and many more, and most of those things on each carriage seperately). This resulted in only 14FPS as reported by the game, but it felt more like 8FPS or so.
I have a Logitech G15 keyboard which has an LCD, and it allows me to monitor CPU/RAM and video card load on it.
The strange thing is, all CPU cores were busy, but the total load was only about 60% maximum at all times. The video card was only on 30% load (possibly an important note, the memory was full, which is however not unusual for the game in question). The RAM had plenty of room and there weren't many operations as it didn't grow or shrink much.
I just have the feeling that the game would run smoother if it used more of my hardware power. Why is it not doing so? I had the same in another game, The Elder Scrolls: Morrowind when using more than 100 mods (that all use scripting) and a few high res texture mods, + a full-on graphics improvement program. The engine is very old (2003), and so I thought this might be the cause (not being optimised for multithreading).
I had thought of possible causes, like:
The operating system doesn't let the games use all the resources.
It doesn't make use of multi-threading appropriately.
To eliminate the former, I tried a CPU stress tool and that got 100% CPU juice as I let it run, so the OS is not the problem. I gave its thread the "higher" priority though.
My actual question
In both games, I did things the engine was not really built to do or support. Can those games' framerate be limited cause of their own engine not being able to cope? What is the real reason and more importantly, can I help it? And in any case, could something actually be wrong with my hardware? It's all reasonably new, a couple of months, and I (almost) never experience any other trouble. Modern and much more demanding games work absolutely fine.
Specs
CPU: AMD Phenom II 965 X4 @ 3.4gHz
RAM: 8GB of DDR3 RAM
Video: MSI GTX560 (nVidia chip) with 1GB of GDDR5 memory
OS: Windows 7 Ultimate 64 bit
Nothing overclocked.
