Q. I'm using Process Explorer and I see different CPU usage from that what Task Manager shows. Why?

A. I heard reports of the different values for CPU usage for processes and the total CPU use for the system between Process Explorer and Task Manager. You can see this in the following image:

Take note of the total CPU Usage values, which show nearly 4 percent difference. Both System Idle and iexplore.exe are also quite different.

Process Explorer is actually showing the true CPU usage, which is found using new CPU accounting features added in Windows 7 and Windows Server 2008 R2. These features track all CPU usage of threads on the system. Task Manager simply checks the CPU usage at timer ticks (normally 15.6ms), which are very small but still miss any CPU usage in between the timer ticks. The processes using CPU at the time of the check are assumed to have used the CPU for the entire timer tick duration. While Task Manager is good for most use cases, if you want the exact values Process Explorer is your best bet.