Dual Channel even with 3rd DIMM?

[DenonSix]

I currently run my NF7-S 2.0 with 2x256 PC3200@400mhz in Dual Channel mode....

I really want to upgrade to 1 Gig since Star Wars Galaxies sounds like it could really use the extra storage...

Do I have to scrap the 2x256 for 2x512 or can I just add a 512 stick (identical specs as the 2x256) in the 3rd DIMM slot?

I heard you could still run Dual Channel @ 400mhz but it will only be dual channel for the 2x256 while the other 512mb will run in regular mode @ pc3200 speeds? Is this true or am I out of luck?

[TxAMD]

I think you would want to run dual channel in slots 3&2, then 512mb in slot 1....i think thats how it goes.

[Reefa_Madness]

That is correct, put the largest stick in the single slot, that amount x 2 = max ram which can then be accessed by both memory controllers concurrently. In this case 512 x 2 = 1024MB in dual-channel mode.

[Cerberus2k7]

If you're using two or more modules of unequal size, you will get the best performance if you put the largest module(s) (in megabytes) in the lowest-numbered slot(s). For example, if your system currently has 256MB of memory and you want to add 512MB, it would be best to put the 512MB module into slot 0 and the 256MB module into slot 1.

Using Dual Channel

Dual Channel requires at least two modules for operation. It is recommended that the modules you use be of the same size, speed, arrangement etc. Dual Channel is optional on the original nforce2 motherboards and nforce2 ultra400. You can choose to run in single channel mode on these motherboards. Nforce2 400 boards are singe-channel only. Most dual channel capable nforce2 motherboards come with three slots. On these motherboards the first memory controller controls only the first slot (or the slot by itself), while the second memory controller controls the last two slots (which are usually closer together). Name them slots 1, 2 & 3 respectively. To implement Dual Channel, it is necessary to occupy the slot 1 (channel 0) and either one of the two slots that are closer together, slots 2 or 3 (channel 1). The entire config would be running in 128 bit mode.

You can use three modules in Dual Channel Mode, by filling the third unoccupied slot. With three sticks, slots 1 remains as channel 0 while slot 2&3 become channel 1. To maintain 128-bit mode, with all three slots filled, each channel must have an equal amount of memory. For example, slots 1 should be filled with a 512 Mb module, while slots 2 & 3 are populated 256 Mb modules. If you were to use three modules of the same size, then only the first two modules would be running in 128 bit Dual Channel Mode. Example, using 3x 256 Mb modules will have the first 512 Mb running in 128 bit Dual Channel mode, while the remaining 256 Mb will be in 64-bit Single Channel mode.


Does that help any?

Taken from the Memory Basics Sticky