Quick question on adding RAM

I just have a real quick question regarding some RAM that I just purchased, 1 gb ddr400 (2X512 MB) to run in dual channel mode. Can I add this to my existing RAM, 512 MB ddr400 (2x256 MB) already running in dual channel? I have enough slots, I was just wondering if this was feasible in dual channel mode. It would be no big deal just to remove the existing RAM, but I would be very pleased if I did not have to.

Thanks guys, sorry for the newbie question,
Eric

Sure you can do this. As long as the motherboard has 4 slots and all the memory has the same specs. You need to make sure you install the new ones in slots 1 and 3 then install the old ones in slots 2 and 4. After this the system will be running in dual channel module with all four modules.

Crucial Performance Lab

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cpl@micron.com

Thanks for the quick replies!

I have an intel 865gbf motherboard with, as I said, 4 available slots.

Thank you again!

Crashman is absolutely correct. I posted a topic about this earlier but there were no good responses.

The answer, though it is not explained too well, is found at (look at the last page):
ftp://download.intel.com/design/c [...] 273001.pdf

To Sum it up:
Basically, for the i875P chipset the Memory Controller Hub configures the memory address lines differently for a given arrangement of DIMMS in the slots:

For two SS (single sided) DIMMS occupying a channel (2 slots/channel)
OR
For a single DS (double sided) DIMM occupying a channel,
A[19] is used for rank selection
A[20] used for regular row address bits on the memory bus.

For two DS DIMMS occupying a single channel, both A[19] and A[20] are used for rank selection.
This configuration offers faster performance.