At the bottom of the page you can see 2 examples of DDR3 routing.
Why should the routing for a Registered DIMM be any different from an Unregistered one?
Because Registered DIMM uses extra Buffer/Delay chip because of that Controller won't see much loading effect of the memories. Data transfers will be reliable.,
Because Registered DIMM uses extra Buffer/Delay chip because of that Controller won't see much loading effect of the memories. Data transfers will be reliable.
Because REGISTERED DIMM involves extra chip --> So, traces will go to this Chip as input and output may be 2 sets will be transferred to different sides.