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Task Manager reports that my CPU frequency never goes higher than about 1.93 GHz. Correspondingly, my CPU usage never goes above about 91%. I downloaded a program called "Speccy" to verify this and was surprised to see that it reports my CPU's frequency as 2.092 GHz when under a heavy load:

CPU frequency reported in Speccy and Task Manager

This CPU is in a Sony laptop (VGN-NW220F). The CPU is an Intel Pentium T4300. The OS is Windows 10 Pro, 32-bit.

Why does Task Manager report an incorrect frequency and CPU usage for my laptop?

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Task Manager is not reporting an incorrect CPU clock speed. According to Intel, that processor is 2.1 GHz. However, that is really the marketing department just rounding it up. Speccy says its 2.092, which is the actual top speed.

Task Manager is showing a lower frequency, as that processor has SpeedStep. SpeedStep lowers the speed of the CPU when the highest speed is not needed. It does this in order to save energy and reduce heat.

In your screenshot, the CPU is running ~90%, but your disk is at 100%. This shows that whatever you are doing is actually being slowed down by your hard disk, not the CPU. There is no reason to run the CPU at its highest setting, if the disk is not able to be read or written to fast enough.

  • When the CPU frequency reduces due to Speed Step, it's reflected in both Speccy and Task Manager; they will both show a reduced frequency, and they tend to agree with each other. However, when the CPU is at full load, Task Manager never reports a frequency above 1.9 GHz. The system was not I/O constrained at the time of the screen shot. Prime 95 doesn't need I/O to fully load a CPU. I could upload another screen shot to show that, but just take my word for it. – Kurt Tomlinson Sep 21 '16 at 2:11

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