The RSP performs two functions to support programming the RDP: segmented address fix-up and handling setothermode.
Segmented Address Fix-up
Since the RDP is a physical address machine, the RSP must translate the segmented addresses present in the display list into physical addresses for the RDP. It does so by filtering out any RDP command with an address (the 'set image' commands) and patching the address before passing it to the RDP.
The RDP setothermode register is a collection of state bits, affecting many different functions of the RDP. In order to simplify programming the RDP state, the RSP caches the SETOTHERMODE command, and presents a simpler "set/clear" interface through the display list. Please see Section 12, "RDP Programming" for information about the macros.