The idea behind CNR is to integrate the networking chip's data pump into the core chipset, but have the physical layer part onto the riser, in order to offer a choice of 10/100TX "real" ethernet or 1/10 MB/s home phone networking with the same core chipset.
IMHO, stupid idea. Now that chipmakers involved in Ethernet stuff have slowly and painfully integrated their stuff into cost effective single-chip solutions, VIA and Intel switch back to using external PHYs. These are expensive.
SiS 540/630/730 all-in-ones, in turn, don't follow that idea. They plain and simply have the entire ethernet unit integrated, with two PHYs for 10/100TX or Home networking.
Now to the software support - as long as the controller device is supported, an operating system doesn't have to take care of how the physical connection looks. The PHY device hangs off the controller's circuitry, and is handled by the latter. No difference in software.
Like if VIA should pull the controller half of their Rhine 10/100TX chip into a new superduper-southbridge, software will still see it as a Rhine. Likewise, the integrated Ethernet in said SiS chips still looks like a separate SiS 900 LAN device to the software.
Regards, Peter