So I am building a PC and I am wondering about upgrading in the future. I know that I want to go with a gtx 760 for my video card but I know that I will want to add a second in the future. My question is that if I buy a 2gb 760 now, can I buy a second 4gb 760 and still take advantage of the 4gb of v-ram? I know v-ram doesn't stack so if I used the 4gb card as the primary top card will the system use all 4gb of ram, I'm worried that it would only use 2gb or not work because there different EVGA cards (4gb vs 8gb).
just go for the 2 gb 760 If you go with 4gb it could actually cause a bottleneck on the gpu. so when you have them in sli there is 4 gigs total, which at this point doesn't matter unless you are running very high resolutions.
The way it works is say you had two 2gb cards in SLI, windows will say you have 4gb of vram, but in reality you only have 2gb. When things are loaded in to vram they a mirrored on both cards to save pci-e bandwidth. So if you had a 4gb card and a 2gb card then no matter which was your primary you would only have 2gb of usable vram. It also might not work at all, I'm really not sure about that.