Command-line CPU frequency scaling?

How to configure Ubuntu 12.04 Server to dynamically adjust CPU frequency during quiet times?

I've found a set of instructions at http://ubuntuforums.org/showthread.php?t=944190, suggesting to add acpi-cpufreq to /etc/modules, modprobe it, and then put one of (powersave, performance, ondemand, conservative) into the /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor files.

But on my system, those files don't exist:

user@pc:~$ ls /sys/devices/system/cpu/cpu0/
cache        microcode  subsystem         topology
crash_notes  power      thermal_throttle  uevent

There's an empty directory at /sys/devices/system/cpu/cpufreq, but

user@pc:~$ sudo echo conservative > /sys/devices/system/cpu/cpufreq/scaling_governor

gives error:

-bash: /sys/devices/system/cpu/cpufreq/scaling_governor: No such file or directory

Intel Atom CPU, if that makes a difference.