Changing the number of CPU Cores running

Question

Changing the number of CPU Cores running

I want to change the number of cores the CPU uses. One minute I might want all 4 cores running the next only 1 core then back to 3 for example.

I have searched in the hope there was a terminal command that would reduce the cores, not at restart but immediately.

Is anyone aware of one?

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I can succeed using Xcode/Contents/Applications/Instruments.app/Preferences/CPUs giving me a slider to change the cores.

When the slider is clicked with the mouse to change the number of cores it requires user and password.

I have managed to run most of the process with Automator/AppleScript but this request for user and password is proving difficult.

In order to avoid it asking I have tried:

entering <DevToolsSecurity –enable> in Terminal; and

put both Instruments.app and XCode in

System Preferences/Security & Privacy/Accessibility

without effect.

Is there a way to avoid this request for user/password but still have the slider change the number of cores?

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Any other suggestions for changing the number of cores at any given time, not just for a process but the complete computer, would be welcome?

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Imac, MacOS Mojave

Earlier Mac models

Posted on Aug 16, 2023 4:50 AM

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Answer 1

Aug 16, 2023 6:00 AM in response to dialabrain

I agree strange request but obviously it is important to me.

Also Apple must think it worthwhile as it has put it as an option in XCode.

Despite you being unable to think of a good reason, as you are a Level 10 with expertise, can you provide any solutions to my questions?

Thank you in anticipation for your helpful reply.

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Answer 2

etresoft

Level 9

51,430 points

Aug 16, 2023 6:31 AM in response to Need_help_give_help

Need_help_give_help wrote:

Also Apple must think it worthwhile as it has put it as an option in XCode.

It is worthwhile in Xcode because so that developers can test multithreaded code on a different number of processors. Otherwise, the developer might not notice a performance problem on their 24 CPU computer when it is running on a quad or dual core.

Also, you seem to be running on an ancient version of Xcode. Apple has removed that CPU option. The whole idea of multithreaded code doesn't have much meaning on modern computers.

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Answer 3

Aug 17, 2023 1:13 AM in response to MrHoffman

Thanks MrHoffman for taking the time to respond. Yes hypervisor isn't the same thing I am trying to achieve.

I don't understand: “macOS doesn’t allow this sort of access into the scheduler past Xcode Instruments.”

as, to clarify, I am able to change the cores in Xcode/instruments/preferences/cpu.

I am hoping to get rid of the request for user and password by allowing perhaps XCode or Instruments some special permission so it doesn't ask for the user/password when I select the core/slider.

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