Cpu never reaches 100%, stops at 92%

I have got an old pc that I am trying to make use of with windows 10 64bit. It has an Intel e5400 cpu. When I run a cpu stress test to check my cpu, the cpu usage in task manager stops at 92% and not 100%. Why is this happening? Regardless of the temp that the cpu is at, it will never reach 100%.
Asked Mar 07, 2017

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