Quote:
Originally Posted by SKUD
Clearly my 590 is not using all the 3GB of VRAM it has in COD because I can directly compare it to my 3GB 580. So my question again is why would Nvidia build a card that can't use half of its VRAM under any circumstances? If this is the case then a 590/690 is nothing more than a 580/680 with a bonus space heater attached.
Never mind... my friend Google found this Gem.
"Originally Posted by CousinVin
I think i understand that putting two 3gb cards still only limits you to 3gb of usable vram.. right? If that is wrong please correct me.
You are correct.
Quote:
Now my confusion comes in with the GTX 590. It is labeled as a 3gb card, but from the assumption above, and considering that it is 1.5gb per core, is it really only 1.5 gb usable vram?
It's marketing. Joe Average can't tell the difference between total memory and dedicated memory."
So anyone looking at the 690 beware.
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Yup, that's how it works. Each GPU needs its own RAM regardless of whether you have two cards with a GPU on each, or a single card with two GPUs on it (like the 690 i think). Also, each RAM has to store the entire frame before it's displayed, regardless of the SLI method used (either card 1 renders frame 1 and card 2 renders frame 2, or each card renders half of each frame).
So, when you see a single card with a dual GPU specifying 3GB of RAM on the box, what it means is 3GB divided equally among the two GPUs and mirrored for each frame -> 1.5Gb of effectively usable video RAM.
If your preferred games are heavy on textures and have long viewing distances (more textures need to be loaded per frame) it's better to go for a single 3GB card or two separate cards with 3GB each. View distance is probably the main reason that players of action and shooter games get great performance with SLI. Their view distance is nothing compared to a flight sim so this RAM issue is not so perceptible.
In the above 3GB example, to load the textures that the single card or the two-card SLI setup can, an single-card SLI setup like the 690 would have to have a total of 6GB of RAM (3 for each card).
I hope i didn't make any typos to make this confusing (it's a bit late at the moment and i'm sleepy) and that it sufficiently explains the limitations of the architecture in terms of RAM usage. Cheers
