James is pretty much right. Here's some more background if you're interested:

http://en.wikipedia.org/wiki/Dual-channel_architecture

One gotcha is: "Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module."

On a side-note, it depends how much stock you place in reviews from Toms Hardware, but theres a link from wikipedia to an article that "found no significant difference between single-channel and dual-channel configurations in synthetic and game benchmarks (using a "modern" system setup)." I thought that was interesting.

YMMV


On Mon, Mar 31, 2008 at 3:03 PM, Daniel Richards <kyhwana@gmail.com> wrote:
James Pluck wrote:
> Hi all.
>
> I thought there may be a memory expert out there in WLUG land :)
>
> Is it deemed a good idea to mix DUal channel with non-dual channel ram in a
> machine with 4 ram slots?  I currently have 1 gb of ddr2-667 ram and was
> looking at getting another 2 gb but I'm not sure if it is worht getting dual
> channel ram and running the dual channel in one pair of slots and the single
> stick in one slot of the other pair.
>
> Enquiring minds and all that :)

There's no such thing as "dual channel ram".
What happens is that you install the ram in "matching pairs" (ie,
2x1GB+2x512MB will work in newish board, I believe) which have the same
speed/timings and the board will automagically run in dual channel mode.

If you install just one stick or 3 the board will run in single channel
mode. You can't run 2x1GB+1x1GB in dual channel mode, it will just fall
back to single channel.

(I think that's right)
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