|Uh...Guapo, what are you talking about?|
System RAM really doesn't have anything to do with this, although the Onboard Memory of the Graphics Card could play a role.
So if I understand correctly, you have to monitors that you would be gaming with, and then just a TV.
I could see why your friend would say that. Basically, when you have one screen, the cards take turns rendering each frame. When you have two screens, each card is dedicated to one screen. Three screen setups are basically a combination of these, two screens each have a dedicated card, and the third screen alternates between each card.
Technically, having an extra screen that isn't being used could slightly reduce performance, as it does require a minute amount of GPU time, but I doubt your overall FPS would be noticeably be reduced.
Your main problem would be how Windows or the game determines which screen gets which card.
Lets say screens 1 and 2 are the gaming screens, and number 3 is the TV.
If one card is dedicated to 1, and the second card is dedicated to 3, the second card has much less strain on it. Thus, when the two cards go to render screen 2 (remember, they each do every other frame) it will take the first card much longer to create it's frame. This can cause something called Micro-Stutter.
Ideally, each card would have it's own gaming screen, and they will share screen 3. That way each has to work just as hard, and it should eliminate the stuttering...but you really can't be sure.
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