You're right, I was also finding this odd. Damn I've been misled so many times recently by lack of good reviews around the web...
I was wondering how RDRAM has 1 byte of data path, it just didn't make sense.
Thunderbirds in wintertime, Northwoods in summertime!
I'm fairly certain that each RDRAM module is arranged with two separate 8-bit pathways, which are parallel to each other, and serial to other modules. Kind of makes since, since DIMM means "Dual inline memory module" or something like that.