I had 2 x GTX570's (1.28GB versions) and ran them @1080P maxed out on BF3, I recorded VRAM usage of over 1200MB's constantly, 1.28GB of VRAM would not be enough for 3 x 1080P monitors if you want to play @ max settings or near max settings.
Thanks for the reply omgitzfatal. What about the same thing, only GTX 570 3-way SLI? Still all three 1.2GB.
Tri SLI would be enough horse power for Maxed out BF3 but I'd bet good money that you'd experience lag spikes and frequent drops in FPS due to textures having to be swapped between system RAM/HDD and the graphics cards.
Vram is not a problem. Nvidia were clever. The only card powerful enough to utilize 3Gb or more that the 1.5gb ram is the Gtx 580. The 570 shows a performance decrease with the larger bandwidth in games like Crysis 2, Metro etc etc. Its processor just isn't powerful enough to utilize the extra bandwidth. Same with the Gtx 560ti. 2gb ram on it would be a waste as they're processing unit isn't powerful enough to utilize that amount of bandwidth