Genlock (i.e. generator lock) is where separate video signals are synchronised using a reference signal.

This is essential when you are mixing video signals. However there is no need to reference the input in Catalyst. If you are using a scan converter to convert from DVI out of the Catalyst into SDI or HD SDI to feed into your Ross then you will need to genlock that.

When I worked at XL we dabbled with Genlockable graphics cards.
http://www.rpaelectronics.com/Genlock/genlock.html
The idea here is to synchronise the signals leaving the DVI output between computers.

Hugh