double vram cards in xfire/sli

please re-read my post, i already stated what you just said, and i am aware also that under perfect conditions, optimized drivers etc, that scaling is about 1.8-1.9 with 2 cards, not the same as just one bigger one.

ok, sorry about the run on sentence, but once again, i stated please dont tell me to just buy the bigger card, that is not the question or the solution im looking for. so to clarify, the bus denotes the connection between the gpu and vram, correct? so yes, the 1280 stream processors on the 270x will not push the 4gb, the 2816 of the 290x will push that much vram, and yes 2560 (1280*2) is less, but not by much and since, ideally, in xfire each card is only working half as hard, thus not needing to think as much to keep up with each other, is the extra vram a viable option in xfire? it might not help it perform like that (once again) $500 290x at higher resolutions, but will it make a difference in that type of setup to where it might perform like one at a resolution, say 1440p? i dont think i would say it could hande a 4k, but i am just grasping at straws now trying to make my question clear.

right, but each card has to work only half as hard, and vram also matters for effects(more frame buffer) not just texture info and meshes, like fxaa; for instance i believe in multi gpu setups there is a way to extrapolate a higher anti aliasing by the way it renders the frame between the two cards, i know i have read that before but is it still used? it could have been an nvidia trick and not aplicable to this radeon example(or a reason to swich this example to an nvidia setup......).
another example to help me understand this, if it were possible to 'hyperthread' the 290x down to 1408 streams and 2gb, yes its still better then the 270x but its only working half as hard, and shouldnt this depend more on fillrate and textel rate?

thank you for your input, sorry for the convolutedness of some of my questions and examples... thus thanking you for your patience as well.

as for multi gpu aa; http://www.nvidia.com/object/slizone_sliAA_howto1.html, and http://www.nvidia.com/object/quadro_sli_fsaa.html, knew i had heard somthing like that. dosent looks like it applies but knew i had read it, and any aa method adds to that frame buffer, thus vram usage, but is useless if the card cant push it, which is why most reviews limit themselves to 4x aa, at that point you are trading framerate for image quality by a good margin (depending on setup), and as you said one 270x can't push 4gb, but can 2?

yes, i am aware of no 'hyperthreading' on gpu's, thus the quotes and it was just an example referencing intel's method of splitting the core in 2 for more threads, with 5800 something cores in a 290x that would be one heck of a hack job...... odd example(back of the hand slap, ouch...)

so far you are understanding the question the best; does the extra vram help in xfire?..... would it matter or are these companies just wasting the memory chips just to earn a few extra bucks? as an example, toms hardware review of 2x r9295x2's in quadfire, it repeatedly mentions hitting the vram ceiling on a few games, so in that case, hypothetically speaking....., what would it need? that's sort of where i thought of this. i think without any real world tests (hint hint tom's) which i agree are the best, this is just a bunch of speculation and thats that.

why there are no benchmarks is a good question but i like 'pushing the envelope' of whats possible and this site has answered many questions over the last couple of years ive come to it, much respect for its methodology and mindframe, and enough so that i finally joined when i thought of this just because SOMEONE on here might have an answer thats definitive, have that type of setup and be willing to run some gpuz tests. at this point im not going to pick a best answer, but i think id like to leave it open just as a sort of sticky until a benchmark is made, but between my bad diction and your noteworthy answers what else can be said until said benchmark. thank you for your time k1114 and when i win the lottery or that rich uncle of mine that i dont know about leaves me his inheritance i will waste the money JUST to answer this and let you know, real world style