Powernowd seems to be working well for me so far, it has a few sane modes:
- aggressive
- passive
- leaps
Yes, this is able to do what I'm looking for. I use these settings with Everex Notebooks:
OPTIONS="-n -p 10000 -u 30 -l 4 -q"
This makes the CPU easily jump to top speed, then slow down over a long period of almost complete idle cycles.