You know when you run dual GPU's your system recognizes the VRam from only one of the cards right?
But anyway patch 1.2 is supposed to address issues that are apparent in dual GPU systems.
[Edited by Methose, 11/12/2014 4:49:54 AM]
It uses the VRAM from both cards, but because each card is doing alternate lines, each card is using it's own VRAM. The performance effect is that each card is only filling half of the screen, though with only it's normal allotment of ram. After the processing, you usually get a 30-40% boost in frame rates.
Of course, having a game optimized for it is a big factor. I've played both optimized and non-optimized. But when a game is optimized -it's sweet!