Simple answer: because it doubles your memory speed.

Explanation: memory chips are pretty much limited to running at 200MHz. By
some clever architecture changes made my the RAM manufacturers, it is
possible to both write and read in the same clock cycle, so the memory
modules effectively run at 400MHz. This is still half the speed of the
processor bus (800MHz) and is a bottleneck to processor performance. So by
changing the method of addressing the memory, it is possible to run two
memory modules on a single 800MHz bus, alternately addresses each module per
clock cycle - Dual Channel!

What's it worth in raw performance: 12% for very little additional
investment (if you want dual channel 512MB memory, you have to have 2 x
256MB modules which are just a little more expensive that a single 512MB
module). The processor also costs a little more but also get hyperthreading
enabled on the processor which is worth up to 8% depending on what you are
running.

You may not think that you need all that extra power, but think two or three
years ahead and you may find that the extra 12% wards off yet another
replacement PC for an extra year.

--
Terry Farrell - Word MVP
http://word.mvps.org/

"sf" wrote in message
oups.com...
: Sorry about those empty posts. Don't know how they happened - Google
: "groups" is a dark and mysterious process. I'm posting from Google
: because my home computer died and I haven't decided on the options I
: want for my new one.
:
: If anyone is in the mood to b helpful, I need advice about basic things
: like dual channel SDRAM.
: :/
: I know what SDRAM is but why would "dual channel" be something I might
: need/want?
:
: TIA
: sf
: