Because code is designed to use what it can, and begins paging or other activity, to compensate for less VRAM. If it assesses there is more VRAM, it opts for that path. If it sees there less VRAM, it chooses a different path. What is the basis of the preference for more VRAM--IOW, what is the trade off the programming makes to always opt for more VRAM use when it's available? I don't fully trust subjective impression either, so when one says things appear the same, they are the same. How does one measure 'smoothness', to what resolution? Is it possible making maximum use of VRAM is indeed a way to improve total efficiency, and that also could lead to better smoothness. I'm sure the math can be done to some level of precision to be able to estimate what value more VRAM utilization has over less, and that really is where the answer lies to this question, the math.

Agreed Noel. So then, why go out and buy a 1000 dollar video card to get 6Gb?

Good discussion.

I run triple monitors using two GTX 680s. Frame rates are ok, but not great, and complex scenery or heavy clouds causes performance to plummet.

 

Would I expect to see much performance improvment if I upgraded to dual 780ti's?

Agreed Noel. So then, why go out and buy a 1000 dollar video card to get 6Gb?

The same reason I went out and bought a decent hexacore CPU PCIe 3.0 compliant, 32Gb of 2400Mhz quad channel DRAM, and even a good SSD.  I wanted the headroom, the least number of restrictions so that timing becomes less critical.  I wanted something that had a decent chance of running whatever came along be it V2 which was yet to be released.  Because 6Gb of GDDR5 over a 384-bit bus is a lot of bandwidth & capacity, and bandwidth is generally a good thing--and apparently the programmers made a decision to look for the bandwidth and use it, w/ backup mechanism to help the sim run when the ideal hardware isn't there.

Good discussion.

I run triple monitors using two GTX 680s. Frame rates are ok, but not great, and complex scenery or heavy clouds causes performance to plummet.

 

Would I expect to see much performance improvment if I upgraded to dual 780ti's?

 

Wait till it officially supports SLI and see where you stand... You have two cards but that second one isn't scaling at all yet..

 

 

difference as far as?

The difference for me was the sim was smoother and I could tick the sliders to the right more and maintain decent frame rates.

I'm using only one display 1920x1080. Don't you think 7803GB will be better choice for me than 7704GB?

That was the choice I made. Tough call, though, given the extra cost. Is it worth $100 for 15 percent or so more performance? I think so, but others may differ. The 770 offers more performance per dollar.