DDR2 2GB + 1GB - dual channel?

[Slickone]

Building a PC for a relative and have a 2GB stick and a 1 GB stick, both Kingston ValueRAM. Would it be better to just use the 2GB, 2GB+1GB, or would it be worth buying another 2GB?
Motherboard is a GIGABYTE GA-MA785GM-US2H, CPU is a Athlon II X2.
Not sure yet if it'll be running XP or Win7 (and not sure if 64bit).

I've read that some chipsets (maybe just Intel?) can, for example in the 2GB+1GB situation, run the 1GB + 1GB in dual channel mode, and still make use of the extra 1GB in single channel mode. Will the 785GM?

Also, my memory is foggy...if buying another 2GB, does brand matter?

 

[Blain]

It would be better to simply buy another Kingston VR DIMM of the same specs and be done with it.

 

[VirtualLarry]

Just throw them in. 3GB is better than 2GB, for certain. Whereas, the gain from single-channel to dual-channel is very minimal on AMD chipsets, even when you are using the onboard chipset graphics. (They don't show the same gains that LLano does with faster RAM.)

(I benchmarked a 780G or 785G chipset, and it scored 500 more 3DMark (I think 01) with dual-channel. So, 10,500 rather than 10,000. Not much difference.)

 

[Slickone]

Just throw them in. 3GB is better than 2GB, for certain. Whereas, the gain from single-channel to dual-channel is very minimal on AMD chipsets, even when you are using the onboard chipset graphics. (They don't show the same gains that LLano does with faster RAM.)

(I benchmarked a 780G or 785G chipset, and it scored 500 more 3DMark (I think 01) with dual-channel. So, 10,500 rather than 10,000. Not much difference.)

Thanks for giving a complete and helpful answer, VirtualLarry (something not everyone tries to do). That's probably what I'll do. Just curious though, does that mean for sure none of the RAM will be in dual channel mode with 2GB+1GB?

 

[VirtualLarry]

Just curious though, does that mean for sure none of the RAM will be in dual channel mode with 2GB+1GB?

I'm not 100% sure on that. I know with recent (last 5-7 years) Intel chipsets were capable of running in a partial dual-channel mode.

I think that if you can set your memory channels to "unganged", then they will have two seperate 64-bit memory channels, operating at the same time. One would access 2GB of space, and the other 1GB. So it would basically be like dual-channel.