Go here to learn about the difference between RDRAM and SDRAM....

http://www.hardwarecentral.com/hardwarecentral/reviews/1787/1/

In short, yes RDRAM is faster, and on pentium 4s even faster(no arguement about taht, RDRam systems beat out the DDr, but tahts because its dual-channel RDRam and the DDr is run single like all other RAM types). RDRam has a higher latency and lower bit rate(16-bit).