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I had notice a strange problem on my Dell Latitude E7440. Sometimes the CPU frequency never goes above 1.0 GHz (even when running some cpu intensive program, such as MATLAB), and the computer runs quite slow.

The laptop had an Intel i5 4210u CPU inside. The operating system installed is Windows 10 Enterprise 64bit. This problem can arise even when the computer is kept awake, and several minutes before the occurrence of problem the CPU frequency can rise up to 2.4GHz.

First I suspect the computer is overheating. However after using 3 different software I found the temperature is normal, and the fan is running. Another possible cause is the power supply to the laptop is not enough, but the AC adapter is the original one with 65W output, and I think this is enough for a laptop.

I had used Intel Extreme Tuning Utility to see if any CPU throttling is on, but when the problem arise none of thermal throttling, power limit throttling and current limit throttling is on. Another strange phenomenon is if I use the CPU stress test in this program the CPU frequency can rise to 2.4GHz, but after the test the CPU frequency is still kept below 1 GHz.

The power plan I am using is "Balanced", and the maximum CPU usage is set to 100%. If I switch to "Performance" the CPU frequency rises instantly to 2.4GHz, and the speed of the computer recovers. Sometimes switching the power plan to "Performance" and switching back to "Balanced" solves the problem, but sometimes not.

I have checked the drivers on Dell website, and all my drivers are up-to-date, my BIOS version is also up-to-date.

Any ideas of how to find the cause of this problem, and how to solved it?

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Even though this is an old Question, it doesn't have any Answers, so I'm going to post a link to another Question that might provide insight to others looking at this Question:

CPU giving 1/3 performance compared to same CPUs

The accepted Answer to that Question, which was posted by the OP after solving the issue, was that he was using a 65 watt PSU instead of the original 90 watt that came with the laptop. Once they changed back to the 90 watt, the speed came back.

@zhouyh says the original PSU was 65 watts, but a comment on the Answer to the Question linked above says "Dell is known to be an unfair player, at least when it comes to AC adapters," giving the following link in support of that statement.

Workaround for Dell "Power supply not recognised" issue

I realize this probably doesn't help the OP of this Question. I hope @zhouyh found a similar answer already.

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