What kind of RAM?
 

which kind is the best? ddr-sdram?

Depends....getting an AMD? Then get ddr.

The order from fastest to slowest of the 3 main types goes:

1.RDRAM
2.DDR-SDRAM
3.SDRAM

That is a bit misleading though.

RD RAM, from what I know, isn't compatible with athlons. If you have an athlon, it's best to go with DDR RAM, but if you have an intel, it's best to go with RD RAM.

At the end of the day, I would reckon an athlon with DDR RAM, would out perform an intel with RD RAM, if they were of similar specs.

Well like a few others said, it Depends, if you have an AMDS you can't use RDRAM, if you ahve a P4, use the RDRAM. Recently Intel has taken over (again) in the Chip department and the enw P4's are outselling the new AMD's, so I'd go with the P4 unless you can aford a new comp, and a Mac.