Then OSC will suit your perfectly (you can just use your messages through sockets, if you don't want to use OSC, but I like it personally for many reasons).
Just have one pd sending OSC messages to the other through a port. There's several issues regarding serious sync, but if you feel that its do-able in this easy way.. gor for bingo (as we say in portuguese).
best regards,
Pedro
One to control sound the other to control video (GEM)."(your OS can tell you in which CPU a process is running, there are several cmd tools in linux for that)"