Question on P4T533(-C) and RDRAM

I'm thinking about a new mainboard.
I'm asking myself why you can put only one stick of memory in P4T533 but you need 2 in P4T533-C? Are there different RDRAMs?

Because I don't need Raid, I wanted to by the -C version...what do you recommend?

The P4T533 has 32bit RAM and the P4T533-C has 16bit RAM. I love my P4T533-C and highly recommend it. It only goes to 156 fsb though. If they ever work the bugs out of the P4T533 I would say to get the new revision.