How to Disable a CPU Core

Multi-core CPUs pack multiple processors into a single chip thus allowing multiple threads to run at once. Most of the time, this is a good thing. But at times, for example, when you need to run some legacy applications that are not compatible with multi-core processing, you may be required to disable the cores.

You may also consider shutting down the cores to save on your laptop battery power. Or if you suspect that one of the cores is failing (although this is very unlikely), you may want to test it out by disabling the cores one by one.

Disable CPU Core in Windows

1. From the Start menu, click on Run, type in msconfig and click on OK
2. Select Boot tab and click on Advanced options
3. Tick the Number of processors and select the number of cores you want to use and click on OK
4. Restart your Windows for the changes to take effect

Disable CPU Core in Linux

To disable a core in Linux, you need to be running GRUB.

1. From the GRUB menu, select the entry you want to use and press the e key to edit the entry
2. You will be presented with a few lines of GRUB commands. Select the entry beginning with the word kernel and press the e key again
3. Append the following command to the end of the line:
   maxcpus=1

   1

   maxcpus=1

   If your original entry looks like:
   kernel /boot/vmlinuz-2.6.27-7-server root=UUID=94705e5f-44ab-495c-908a-b23c8b1aabb1 ro

   1	kernel /boot/vmlinuz-2.6.27-7-server root=UUID=94705e5f-44ab-495c-908a-b23c8b1aabb1 ro

   It should now look like this:
   kernel /boot/vmlinuz-2.6.27-7-server root=UUID=94705e5f-44ab-495c-908a-b23c8b1aabb1 ro maxcpus=1

   1	kernel /boot/vmlinuz-2.6.27-7-server root=UUID=94705e5f-44ab-495c-908a-b23c8b1aabb1 ro maxcpus=1

4. Press the b key to boot the Linux kernel. Only one of the cores will be used by the Linux kernel