PC-100 SDRAM refers to SDRAM running at 100-MHz bus speed; PC-133 SDRAM runs at 133-MHz bus speed.
RDRAM is Rambus DRAM, a new type of memory that can run about three times faster than typical SDRAM. The current version supports bus speeds between 600 and 800 MHz, which is why RDRAM is often identified as PC600, PC700, or PC800.
YEAH YOUR RIGHT 1066 .. I got carried away with the 1600 there.
I don't think Rdram is gone at all. Maybe not as popular as DDR, Cost always made DDR look more attractive. Rdram in my opinion in the beginning was more efficient, Rdram now is also going the way of Dimms, Imagine sandwhiched Rdram modules filling your slots (careful people)....now run that with a Hyperthreaded Proc.