VRAM vs FPS

[ManOfArc]

How exactly does more VRAM equate to more fps? From the 'vs' videos I've watched, the 8GB RX-580 (for example) is always 2-10 fps faster than the 4GB version in the same game. I realize that the more VRAM available the more room there is for more frames to be rendered. But isn't the speed that the frames are actually displayed independent from number of frames rendered?

 

[geofelt]

It depends on the game.

A game needs to have most of the data in vram that it uses most of the time.
Somewhat like real ram.
If a game needs something not in vram, it needs to get it across the pcie boundary, at least for the first time,
hopefully from real ram and hopefully not from a hard drive.
It is not informative to know to what level the available vram is filled.
Possibly much of what is there is not needed.
What is not known is the rate of vram exchange;
that is what takes time.
Vram is managed by the Graphics card driver, and by the game. There may be differences in how this is done between amd and nvidia cards.
And differences between games.

 

[atknatmrt]

There are many factors causing that. For instance when we looked at your example 4gb version has slightly less computing power, memory bandwith and memory clock. Another common example is gtx 1060 3gb vs 6gb, similar story here too. So these 'little' things cause that fps difference.

 

[InvalidError]

The main difference with extra memory is that there is more space to duplicate textures and other resources across memory channels to increase availability, even out memory bandwidth utilization and reduce latency.

 

[ThomasKK]

In such comparisons, VRAM is not the only thing that is different between the cards with the same name. As someone said before me, these little things also matter, here i have 2 examples for you:

RX580 4GB vs 8GB (http://www.game-debate.com/gpu/index.php?gid=3879&gid2=3876&compare=AMD%20Radeon%20RX%20580%204GB-vs-AMD%20Radeon%20RX%20580%208GB)
The performance difference is only because 8GB version uses "better" memory if we can call it like that. 8GB version over 4GB version of RX580 has higher memory performance rating, which appears from slightly faster memory clock and bandwidth. Why 8gb rx580 performs better? because it's memory can be accessed a bit faster and more easily.

GTX1060 3GB vs 6GB (http://www.game-debate.com/gpu/index.php?gid=3702&gid2=3656&compare=Nvidia%20GeForce%20GTX%201060%20Asus%20Turbo%206GB-vs-Nvidia%20GeForce%20GTX%201060%203GB)
This is also a popular question. Even though GTX1060's 3gb and 6gb versions both have the same memory performance specs, but the card with more VRAM has more processing power (more shader processing units, texture mapping units and faster texture rate). These numbers aren't very different, but that ~10% difference in raw numbers is exactly what you see in comparisons: 5-10% better performance on a card that has more VRAM.

So, after all, it all depends on the small stuff. Sometimes the VRAM quality can affect the performance and sometimes VRAM has nothing to do with it, you just have to make comparisons yourself to find the real reason why the performance is different. Hope this helps!

 

[ManOfArc]

OK, lots to absorb there. Let me see if a simpleton like me can figure this out.
If 2 cards are otherwise identical... same gpu specs, same exact vram specs/speed/quality, only the amount is different; then they should perform with the same fps?

Add-on question: what does the CPU's "CB" rating in Cinebench refer to? What are CBs?

 

[ThomasKK]

Yes, the fps should be the same if they are identical but with different amount of VRAM UNLESS there is not enough VRAM: for example if you try to play a game that requires 4gigs of vram at 4K resolution, a GTX1060 3gb will struggle, meanwhile 6gb version will maintain normal fps. But that's a different question though, it's not a performance issue, but not enough VRAM leads to screen freezing (fps goes to about 0 from time to time). So, on this you are right.

From me about cinebench: no idea, wait for others to answer, i dont use benchmarking systems often.

 

[dontlistentome]

Another way of looking at it: If everything was exactly the same, except one card had 2gb vram and the other card had 4gb vram, performance would be the same UNLESS the game/resolution/settings used more than 2gb of vram. In that case, the framerate of the 2gb card could be expected to drop, while the framerate of the 4gb card would not drop.

So the cards are still equally fast, but the extra vram on the second card allowed that card to maintain its performance level.