It works for Intel, AMD, ARM and UltraSPARC processors. [1]
However, powertop isn't a power management tool but merely an analysis tool. Any recommended settings you apply with powertop get lost upon the next system reboot. To make powertop's settings permanent you need a tool like TLP (or Laptop Mode Tools). [2]
[1] https://en.wikipedia.org/wiki/PowerTOP [2] http://linrunner.de/en/tlp/docs/tlp-faq.html#powertop
