Limited processor speed is one of the possible causes of slow computer performance.
you’re free to check the CPU status under the Performance tab in Task Manager.
Here are some solutions to assist you in resolving the CPU clock speed stuck issue.

Fix 1.
PressWin + Rto fire up the Run window.
Typeregeditand hitEnterto open Windows Registry.

At the right pane, find and double-hit theStartregistry key.
Change the Value data to4and clickOKto save the change.
Afterward, you should close Windows Registry and kickstart your box to fully apply this change.

Some people report that they have received error alert after changing the value data of the intelppm registry.
Fix 2.
Under theServicestab, tickHide all Microsoft servicesand selectDisable allto terminate all the third-party programs.

Change to theStartuptab and clickOpen Task Manager.
In the following window, check those programs and disable them respectively by right-clicking on them and choosingDisable.
Step 6. end the Task Manager window after operations.
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ClickApply > OKto stash your changes in the System Configuration window.
If the issue is still here, the software conflict is not the reason for your case.
Safe Mode: whats the difference, when and how to use?
After reading this post, you could clearly know all the answers to these questions.
Fix 3.
This is because half the cores are probably missing on your system.
you’re free to read this post to learnhow to reset BIOSwithin 3 steps.
This post explains three solutions that might be helpful in resolving this issue.
you might try them to find one that works in your case.