I put this in my crontab:
This turns three of my four CPUs off between midnight and 8:30am every day.
# save energy by disabling unused CPUs
0 0 * * * /usr/bin/hwprefs cpu_disable 2; /usr/bin/hwprefs cpu_disable 3; /usr/bin/hwprefs cpu_disable 4
30 8 * * * /usr/bin/hwprefs cpu_enable 2; /usr/bin/hwprefs cpu_enable 3; /usr/bin/hwprefs cpu_enable 4
Since each CPU burns a fair number of watts, I’m hoping this will save me some power costs.
I looked for a way to set the CPUs to “power conserve” mode or something in the energy/sleep settings, but no luck.