Neither of us is correct. What happens with multi_driver is:  A new **user_nl_xxx_NNNN** file (where NNNN is the number of the component instance) is generated for every component instance (except CPL) when **case.setup** is called.    without multi_driver:  New **user_nl_xxx_NNNN** files (where NNNN is the number of the component instance) are generated for each for each component with multiple instances when **case.setup** is called.