Processors - Limit Number Used by Windows 7

How to Set the Number of Processors or Cores to be Used by Windows 7​

   Information

If you have a multiple core processor (CPU) or multiple processors, then this will show you how to limit the number of processors to be used by Windows 7, or to make sure that you are using all processors.

This can be handy for troubleshooting and debugging purposes to be able to determine if there is a problem with a single processor/core, or for a programmer to test their code against a single core while still running on their multi-processor/core system.

Windows 7 uses all of your processors or processor cores by default.

   Note

You must be logged in as an administrator to be able to do this.

Here's How: 1. Open the Start Menu, then type msconfig and press enter.

2. If prompted by UAC, then click on Yes.

3. Under the Boot tab in System Configuration, click on the Advanced options button. (see screenshot below)
4. To Have Windows 7 Use All Processors or Cores A) Uncheck the Number of processors box, and click on OK. (see screenshot below)
NOTE: This is the default setting.
B) Go to step 6.
5. For Windows 7 to Use a Specified Number of Processors or Cores A) Check the Number of processors box, then select how may processors or cores you want Windows 7 to only be able to use in the drop down arrow menu and click on OK.
6. Check the Make all boot settings permanent box, and click on OK. (see screenshot below)
NOTE: You will still be able to come back and make changes again if you like.
7. Click on Yes. (see screenshot below)
NOTE: You will still be able to come back and make changes again if you like.
8. Click on the Restart button. (see screenshot below)
WARNING: This will restart the computer immediately. Make sure you save and close anything open that you do not want to lose first.

   Tip

If you checked the Don't show this message again box and would like to restore this Restart box to display again, then see: How to Restore the System Configuration Restart Prompt in Vista or Windows 7

9. When Windows 7 is finished restarting, it will now be using only the number of processors or cores that you specified.
NOTE: You can look in Task Manager (CTRL+SHIFT+ESC) to confirm this number of processors or cores. You will have one graph per core in the CPU Usage History area.
That's it,
Shawn

Related Tutorials

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• How to Set Maximum Memory to be Used by Windows 7 and Windows 8
• How to Change the Displayed Name of the Processor in Windows 7, XP, and Vista

 

[whs]

As far as I understand, this setting is not really doing anything for you. The setting is only there for some testing purposes. But I may be wrong.

 

[Brink]

Hello Wolfgang,

Yes, it's only for testing purposes for troubleshooting and debugging to be able to determine if there is a problem with a single processor/core, or for a programmer to test their code against a single core while still running on their multi-processor/core system.

I also added it for reference just in case someone used this option and forgot about it, and is wondering why not all of the processor cores are being used.

 

[whs]

Good, that clarification is useful. I posted my comment because I have seen guys thinking that it would speed up their system - which, of course, it does not.

 

[Brink]

LOL, yeah I still get people that report to me that they swear that it has improved performance by selecting all processors. I just do not see how though since they are all used by default anyway.

 

[Staple Head]

where do get that all cores are used by default. this is not the case. when you go to msconfig, boot, advance option and it's default setting for cores being used is 1, that is exactly what it is using. changing it 2 or more depending on you cpu makes windows use more cores. various programs you install may or may not use all cores by default, but win 7 does not.

 

[whs]

where do get that all cores are used by default. this is not the case. when you go to msconfig, boot, advance option and it's default setting for cores being used is 1, that is exactly what it is using. changing it 2 or more depending on you cpu makes windows use more cores. various programs you install may or may not use all cores by default, but win 7 does not.

Here we go. No core setting will change that if the program is not designed for it. And the windows kernel needs a major revamp in order to use all cores.

 

[Airbot]

where do get that all cores are used by default. this is not the case. when you go to msconfig, boot, advance option and it's default setting for cores being used is 1, that is exactly what it is using. changing it 2 or more depending on you cpu makes windows use more cores. various programs you install may or may not use all cores by default, but win 7 does not.

Funny, it's using all my cores by default.

 

[Staple Head]

where do get that all cores are used by default. this is not the case. when you go to msconfig, boot, advance option and it's default setting for cores being used is 1, that is exactly what it is using. changing it 2 or more depending on you cpu makes windows use more cores. various programs you install may or may not use all cores by default, but win 7 does not.

Here we go. No core setting will change that if the program is not designed for it. And the windows kernel needs a major revamp in order to use all cores.

what did you mean "here we go"? here we go someone who does not know what they are talking about, or here we go these two lines are my proof? win 7 out of the box when you click on computer it takes about 3 seconds before it list the drives. click on one of the drives and it takes about 3 seconds before it list the contents. when i go in and change the core count to 2 and do the required restart once back in 7 i no longer have this lag accessing my drives and files. i have tested this on a clean install where it was the first thing i changed. i have tested on a clean install where i have installed all of my drivers, software, and performed all of my tweaks then change the core setting. the only time that i actually get rid of this lag is when i change the cores from 1 to 2. nothing else gets rid of the lag.

 

[whs]

"Here we go" was supposed to mean "here we go starting the discussion". Since you were the first poster after Brink and I had the little exchange of ideas, you started the (very useful) discussion. There is a lot of mystery around the full usage of multi cores and therefore this will help us to better understand it.

PS: your observation/setting is interesting. I never tried that.

 

[Staple Head]

then i apologize if i misunderstood what you meant. as for my observations they come from running 7 from the first beta through my purchase of 7. the first thing i noticed when i installed the first beta was this lag. i thought it was just a driver issue. so after the install i did my security software, then i did my drivers. this did not fix it. i tried tweak after tweak to fix it, nothing. one day i ran across an article about the cores, so i changed it from 1 to 2. after i rebooted i decided to click on computer just to see if there was any difference, and the lag was gone. i am a skeptic so i could not believe after all the tweaks i had tried to fix the lag that i had just run across the fix by accident. this is when i ran the various test beds i mentioned. i do not know if others are having this lag or not, but i do know what seems to have fixed it for me.

 

[whs]

There is no need to apologize. Misunderstandings happen - especially from postings made by "foreigners" like me who's native language is not English. Sometimes the intended semantics get twisted in the translation.
But back to your observation. I have never encountered this lag - neither on my 32bit Win7 nor on my 64bit Win7. But if the setting worked for you, you might as well apply it. Nothing wrong with that.

 

[Staple Head]

i have checked forum after forum and searched for this and with the exception of a few no one seems to get it. so i'm thinking that for some reason it is just a odd quark with my hardware setup.

 

[Night Hawk]

Once the new build is together here I will be able to put all of this to the test since I'll be moving from a dual core into a quad core build. It should be interesting to see what the performance monitor and other logs reveal as well as a look at the performance monitor.

As far as speeding things up there was some discussions that taking a single core cpu or dual core model and bumping the number of cores was supposedly resulting in some kind of performance gain there. The idea was put to the test and revealed no notible performance boosts.

That discussion was seen over the last few years on different forums. I tend to agree with Shawn on not seeing any particular gain with that alone. Hope you Digg the guide here just the same!

 

[Brink]

where do get that all cores are used by default. this is not the case. when you go to msconfig, boot, advance option and it's default setting for cores being used is 1, that is exactly what it is using. changing it 2 or more depending on you cpu makes windows use more cores. various programs you install may or may not use all cores by default, but win 7 does not.

Hello Staple Head,

Was the boxed checked with 1 selected?

By default, when the Number of Processors options is unchecked, the number in the grayed out drop down menu is irrelevant. It is only a relevant option to select how many when the box is checked instead.
When grayed out, all processors or cores are available for use in Windows 7. When you check the box, only the number of cores/processors you select will be available to for use in Windows 7.

Now whether Windows 7 decides to use them, programs are programmed to make use of multiple cores or processors or not, and how the CPU affinity for a process is set is another story completely and will affect how many cores/processors are used as well.

 

[Staple Head]

brink i go in and check the box and then it to 2.

 

[Brink]

Well, I'm happy to hear that you say you clearly notice a performance gain by checking the box and selecting them all manually instead of having them selected automatically with it being unchecked. I'm just not sure why or what would make a difference like that. That's all.

 

[whs]

Mysteries surround our life - LOL.

 

[Staple Head]

Well, I'm happy to hear that you say you clearly notice a performance gain by checking the box and selecting them all manually instead of having them selected automatically with it being unchecked. I'm just not sure why or what would make a difference like that. That's all.

Mysteries surround our life - LOL.

mystery is right, because when i setup my roommates system i never see the lag on his machine. the thing our systems are more similar than not.

 

[MadMaxData]

This thread should be removed by an Admin. You should NEVER tell inexperienced users to go messing around in the advanced boot options for how the OS handles CPU's. This setting should NEVER be touched unless you know what your doing. It's one of the few places where the OS communicates directly with the BIOS. If you have a dual core, or quad core CPU it should still be set at 1 by default. Only when you actually have two seperate physical processors should it be set to two. And the OS will do that automatically when installed. Unless you have a problem with your BIOS.

Leave this setting alone!