You can let run the virtuell time of the simulated machine slowlier or faster. So you can analyse critical moments calmly, while you let processes which already run correctly pass by quickly. The precision of the simulation is not influenced by the slow motion or the quick motion, the simulation repetition rate keeps always the value which is set in View|Options|Simulation.
You can also get the slow motion if you click (several times) on the turtle 
.
And you can change the simulation speed with the Speed-Trigger automatically.