ptwaugh,
Turbines have limiters, because otherwise they'd just run faster and faster until something comes apart, or force the pilot to beady-eye the gage almost full time. The simplest limiter is the N1 (or Ng) limiter that is basically a fly-weight governor that stops the N1 from going above its max speed. This looks to the pilot as if the N1 just freezes, and the power (temperature and torque) gets stuck there. If he keeps raising collective, the rotor starts to droop (reduce in rpm as collective is pulled) and the situation can get very serious. If the rpm droops too far, tail rotor control can be lost, the aircraft will start spinning and someone will run from the bushes and call it "LTE" which it is not.
We call the act of reaching the limiter "topping" and on older models, this topping is actually set by the maintenance pilot during the test flight when an engine or control are changed.
On newer models, the electronic governor or fuel control has sophisticated limiters that stop at temperature, torque or N1, depending on which is achieved first.