Well? I was wondering if you could SLI a 2GB GTX 460 with a 1GB GTX 460.
Im going to dabble in a bit of thread necromancy here to clear something up.
As long as the GPU is the same model number it will SLI / Crossfire.
If you have different clocks / memory on each card they will negotiate and downclock to match each other. So if you SLI 1gb and 2gb cards it will work but will both act as 1gb cards giving you a grand total of 1gb vid memory, the same goes for any factory overclock.
So if I had 2x 1280MB GTX 470s, only 1280MB would be used? Leaving 1280MB unused?
In an SLI configuration, cards can be of mixed manufacturers, card model names, BIOS revisions or clock speeds. However, they must be of the same GPU series (e.g. 8600, 8800) and GPU model name (e.g. GT, GTS, GTX). There are rare exceptions for "mixed SLI" configurations on some cards that only have a matching core codename (e.g. G70, G73, G80, etc.), but this is otherwise not possible, and only happens when two matched cards differ only very slightly, an example being a differing amount of video memory, stream processors, or clockspeed. In this case, the slower/lesser card becomes dominant, and the other card matches. Another exception is the GTS 250, which can SLI with the 9800 GTX+, as the GTS 250 GPU is a rebadged 9800 GTX+ GPU.