Explanation for sli not doubling vram

[Kritonios]

Hello, I will be clear and state my questions; First of all, I have searched many articles online and almost all of them are saying that sli doesn't double vram. Some people say that one card renders 2, 4, 6, 8... frames and the other 1, 3, 5, 7... Others say that it does something like mirroring ram and that doesn't double it. But, even though everyone in forums is saying that it doesn't double memory, some people on youtube make videos with games playing them in sli and in many games in the settings have a memory counter in which if for example the title of the video says gtx 980 ti sli, it will show 12gb.
1. I would like someone to explain me what is happening with memory is sli in a simple way
2. If it doesn't double memory how do these people double their vram

Thanks as always and any help is appreciated (don't hesitate to answer part of the question)

 

[Toysoldiers35]

When in SLI you are correct they trade each frame in supported applications. If this makes sense, each card has to store the entire image taking up VRAM from both cards therefore not doubling it. So if you have 2 4gb cards for instance, 1 will store data for one frame which takes VRAM and the other the next frame that also takes VRAM. Your second question is the simple answer of applications don't recognize what is actually happening and defaults displaying misleading info. Hope this helps! It is indeed tricky to wrap your mind around.

 

[Shaun o]

SLI is short for Scan Line interleaving.

One card in an SLI graphics card setup only draws the odd lines of the overall screen image displayed.
Where as the other card in the SLI setup draws all of the the even lines of the image displayed.

Each card used in the SLI setup is in fact only drawing half of the total screen image at any given time, of the overall resolution and bit depth in color of the screen image generated.
Because of this less memory is used from each card, because the screen resolution that each card has to produce is halved. Each display area

The higher the resolution more memory is used on a graphics card, because the pixel density increases per inch of the image being displayed. DPI Dots Per Inch
Each pixel, and it`s color has to be mapped, or should i say its co ordinance of it`s X and Y position on the monitor display. Along with it`s bit depth or color mode. When you hear the term Bit map, or bit mapping. This is what it refers to as what is going on.

Bit depth relates to how many colors can be displayed on screen at the same time out of a palate of colors available.
Again the amount of colors that can be displayed on screen at the same time uses or consumes more memory.

Back in the old days with a CRT, or tube monitor. The image produced was drawn one line at a time from the top of the display to the bottom.

In basic terms 01010101 If you know binary that 0 is off, and 1 is on the display image that is generated is done by switching from one card to the other when required based on if it is an odd- 0 or an even- 1

The memory does not double, SLI is a way of reducing the memory used of each graphics card.
In effect it means you can display more color at higher resolutions, since each GPU is doing half of the graphical, and display output it needs to do.

 

[mlga91]

Hello, I will be clear and state my questions; First of all, I have searched many articles online and almost all of them are saying that sli doesn't double vram. Some people say that one card renders 2, 4, 6, 8... frames and the other 1, 3, 5, 7... Others say that it does something like mirroring ram and that doesn't double it. But, even though everyone in forums is saying that it doesn't double memory, some people on youtube make videos with games playing them in sli and in many games in the settings have a memory counter in which if for example the title of the video says gtx 980 ti sli, it will show 12gb.
1. I would like someone to explain me what is happening with memory is sli in a simple way
2. If it doesn't double memory how do these people double their vram

Thanks as always and any help is appreciated (don't hesitate to answer part of the question)

You already said it, whatever is in one card's memory it will be in the other, thats why is not "doubled", and as for msi afterburner showing 12GB of VRAM, its because in fact, those 12GB (6+6 GB) are being allocated, all the memory will be one pool, but each set of memory will have the same than the other, so, you have the double of the memory, but you have the same on the two sets.