Multicore CPU: how to disable a coreJune 2014

To run certain applications that are not compatible with multi-core operations, it may be necessary to disable acore in a multi-core CPU. In Windows systems, it is possible to disable a core through the system configurationwindow. Choose the number of processors that should be enabled or disabled and restart the computer for thesettings to take effect.Disabling a core in Linux can be done through the grub menu and add parameters to thekernel entry. These parameters are sent directly to the core when the Linux is starting. The Linux system has to berestarted after the modifications to disable a core in a multi-core CPU are made.

Multicore CPU: how to disable a coreProcedure when using Windows (Vista, 7 and XP)Procedure when using Linux

It is sometimes quite useful with a multi-core processor to be able todetermine whether a core is working properly during rise in frequenciesor for testing purposes. This can be done by disabling a core, therebyisolating the potentially problematic one. Sometimes this procedure isnecessary to run certain applications, which are not compatible withmulti core processing. Note that this procedure will not affect physicallyyour hardware, but your OS (Windows or Linux) will simply ignore thecore(s) you selected.

Procedure when using Windows (Vista, 7 and XP)

Open the start menu, click on Run, type in msconfig and click on OKIn the System Configuration window click on the Atart sub menu and the on Advanced Options button

In the second window that appears, you should be provided with an option for enabling and disabling theprocessors as you wishValidate your entry by clicking on OKRestart your PC

Procedure when using Linux

When using Linux the procedure is quite different. When starting up your PC, you should find the Grub menu, whichis responsible for launching Linux. Select the entry you want to use, press the E key and a menu will appear(depending on the version used).

title Ubuntu 7.10, kernel 2.6.22-14-generic root (hd0,5) kernel /boot/vmlinuz-2.6.22-14-generic root=UUID=a8a39729-9d2a-425b-b84b-ecc5c7dad104 ro quiet splash initrd /boot/initrd.img-2.6.22-14-generic quiet

Using the arrow keys, go the line beginning with the word "kernel" and press E again. Be aware that you areediting the line, which defines the path to your Linux kernel (core). At the end of the line, add the followingcommand:

maxcpus=1

The end result should be:

kernel /boot/vmlinuz-2.6.22-14-generic root=UUID=a8a39729-9d2a-425b-b84b-ecc5c7dad104 ro quiet maxcpus=1

Note: que ro, quiet and maxcpus are the parameters sent to the core when starting up Linux. Press the B key tostart Linux.

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