> This eliminates the need for an on-battery or plugged-in performance mode because it changes frequencies so fast, you're no longer losing performance by waiting for the software to speed up the cpu. So you can keep it on all the time.

Here's my /etc/rc.d/rc.local script:

    #!/bin/sh
    for policy in /sys/devices/system/cpu/cpufreq/policy*
    do
        echo "power" > "$policy"/energy_performance_preference
    done

Here's available preferences:

    $ cat /sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences 
    default performance balance_performance balance_power power

Basically I can choose between "performance" and "power" (low performance) modes. I'm choosing power, so my fans are silent. And they're silent indeed, no matter the load.