Number of Utility Load Slots

Hi, 
Some utility load slot questions...
1.  Are there any guidelines for the number of utility load slots a Teradata system can have?  Is there a limit?  How is it determined.
2.  How do we configure Teradata to have more or less load slots? 
3.  Exactly what is a utility load slot?  For example, is it a dedicated AWT?
Jerry