Yes....Effectively it's only a 2GB GPU. Each frame is handled one at a time back and forth between the two GPU's on single PCB just like if it was in SLI.
One huge kudos to the 690 is the 'frame metering' that was implemented on a hardware level. IMO it handles like a single GPU because I don't see the micro-stutter while gaming that I was expecting from a dual GPU.
Yeah when I had a 590, I never experienced microstuttering as well. I love dual core GPUs