Because the cards come with 12GB frame buffer, you should ideally have 24-48GB of system memory, due to the way Windows handles VRAM.
Basically, whenever the VRAM is full, Windows will swap the data onto the RAM, meaning that the 12GB VRAM on the card needs 12GB of system memory as swap space.
I see a lot of people SLIing these, with 12/16 gigs and RAM, and it basically just bottlenecks them, IF it ever happens that you need the RAM.
Was just curious as to why you'd have SLI titan X's with 16 DDR3.
