The TUSL2 is the i815E B0 and will be SDRAM.
But there is the Via Apollo Pro266T or whatever it's called that supports DDR for it. And I'm sure there will be a chipset somewhere that supports RDRAM.
I'll be damned if I touch a Via chipset again, and RDRAM is useless except for the P4 so I'll stay with good old SDRAM.