Dual DDR question

I was wondering if i had 2, 256 meg sticks, and i ran it in dual ddr, would it recognize it as 1x 256megs of ram, but double throughput? or is it double throughput at 512megs of ram?
Thanks

NF2 would recognize it as 2x 256MB giving you a total of 512MB.

Can you have (1) 512MB stick along with (1) 256MB stick in dual DDR, or do they both have to be the same size?

I'm almost positive they have to be the same size. You can have a 512 and 2x256 sticks and still run DC mode. The ASUS manual says which slots to use for dual channel, but it makes no reference to size, but I seem to remember a review saying they had to be the same size (at least the banks used did). So you could have a 512 in bank 3 (channel 2) and a 256 in banks one and two (channel 1) and work in dual channel mode...

Seems workable, whether or not you can run DC with 3 sticks was actually my next question. Thanks.

well, just got my 8RDA+ from the UPS man. Got it up and running now with some older PC-2100 until the rest of my stuff gets here. I'm using 1 512MB and 2 256MB Dimms and it seams to be working fine. Not one of these Dimms is even the same brand as either of the other 2.