Most Games 100% CPU Usage, but nothing is using nearly that much

[The mouse]

Basically the title, I've noticed this issue mainly when playing UE3 games and CoD when after 30 seconds or so the game goes from high FPS to random stuttering and lag, under Task manager it says the CPU usage is 90-100% despite the game is only using 40-50% and the only other thing is Steam or Audiodg which is using around 5%. What is happening and how do I fix it.

My Cpu is an Intel i3 2.4Ghz

[bohb]

All games automatically allocate the largest slice of CPU time to themselves. The reason it's only showing 40-50% CPU usage in the task manager is because you have a dual core processor and Windows combines the total number of cores into 100 percentage points.

So if you have two CPUs/cores, each core will represent 50 percentage points. 4 CPUs/cores will represent 25 percentage points, 8 CPUs/cores will be 12.5 points, etc.

You can see the real processor usage per core in the "performance" tab, it will have each core graphed out separately.

[MTMod]

Sounds like it might be a cooling issue. Can you check your temps when you're ingame?