Sometimes it can be useful disabling CPU cores for testing purposes, for example, if you want to test an application under single-core use. You can change settings within Open Firmware to make your system believe it has fewer processors than the number that are actually present.
You can create the same
cpus setting in NVRAM using the Open Firmware user interface. Once the setting is in NVRAM, the setting persists across system restarts.
To set the number of
cpus within Open Firmware, follow these steps:
- Boot into Open Firmware (Command + Option + O + F during the boot process).
- To view the current
boot-argssettings, enter the following command:
cr boot-args type cr
printenv boot-argswill accomplish the same thing, but will output the hexadecimal value of each character in
boot-argsrather than readable text.
- Enter the number of CPU cores to utilise with the following command:
setenv boot-args cpus=1
- You will need to reenter the current value of
boot-argsif you want to preserve it. For example, if the result of Step 2 was:
The command would read:
setenv boot-args debug=0x4 cpus=1
- After the
okresponse, continue booting your system with the