Considering vram when preparing for a triple-monitor gaming build

[tig2575]

This is a repost from Tom's Hardware, I thought I might get a bit more in-depth discussion on the matter, here :)


I'm planning on building a gaming rig to use either Nvidia Surround or Eyefinity in a 3 monitor 5760x1080 or 7680x1600 resolution display (ideally 7680), and I'm hoping that the cards I end up putting into it will last me for quite a few years with at least adequate performance in games long down the road (not necessarily maxed out).

In researching, one thing I've heard is that high resolution gaming like that tends to run into bottleneck issues with a graphics card's memory. I've been a long time Nvidia customer, and I've always been satisfied with their cards, however I'm concerned with the fact that they always trail behind AMD in the memory department. Even this article seems to hint that Nvidia is (yet again) going to be a full gigabyte of vram behind AMD on their Kepler reference cards.

Is the concern of becoming bottlenecked by limited card memory in the next few years legitimate enough for me to defer to trying my hand with a pair of AMD cards? Or is my understanding of those implications somehow lacking? With triple monitor gaming on a powerful rig, is vram always going to be the first limiting factor for performance?

[BHawthorne]

Yes, games like Skyrim and BF3 are prime examples of how in triple screen mode you can eat up significant amounts of VRAM. It will only get worse as time goes on. It's also why AMD set the baseline at 3GB this time around on the 7980. If you prefer the NVIDIA side of the fence EVGA does make a GTX580 3GB. 2 or 3 of those would work fine for awhile. Even then don't expect excellent FPS in Ultra settings. High settings would be good though.

[scavvenjahh]

Something around the 2 GB Mark is ideal for "regular" 3x 1920 Surround, but 3 GB might come in handy at 7680.
Past 1.5 GB sheer GPU power tends to become an issue before framebuffer size in most scenarios, so don't fool yourself, huge amounts of VRAM won't solve everything - but there are exceptions, and it seems reasonable to think you should go with the most VRAM-laden high-end cards you can find.

Paradigm Shifter's article, although not focused on super-high-end Surround, has interesting data on the subject: http://widescreengamingforum.com/article/palit-nvidia-gtx460-surround-1gb-vs-2gb

[tig2575]

Thanks for the link, man. What's your opinion regarding building a machine with my eyes towards the future? I.e. a machine that will avoid getting vram bottlenecked in current games as well as games to come out in the next 3-4 years? Do you think 3GB will likely be a limiting factor before the rest of my hardware becomes obsolete down the road?

[scavvenjahh]

Well I can only share a gut feeling, but I think 3 GB should be more than enough for at least another couple years... Average GPU power may very well be doubled by then, but I doubt on-board VRAM quantity will.

[Haldi]

Bout 8000x1440 and Vram:
Running 7970 CF. Tested Crysis in Very High settings!
8xAA= 6GB Vram usage and 2FPS
4xAA= 5.8gb Vram usage and 25FPS
2xAA= 5.2gb Vram usage and 26FPS
1xAA= 4.8gb Vram usage and 28FPS
0xAA= 4.2 gb Vram usage and 30 fps.
In 6040x1080 it runs way better, and i dont hit Vram limit with 8xAA

[Paradigm Shifter]

How much system RAM have you got, Haldi?

Also, how'd you monitor VRAM usage above real VRAM?

[Haldi]

I got 16GB Ram.

2x HD7970 in Crossfire = 6GB VRAM. BUT your game will use the double VRAM compared to a single HD7970! So its true ! It doesent increase VRAM its just verry strange readings with all tools! (GPU-Z, MSI afterburner.)

[Paradigm Shifter]

I think that is to do with the way that AMD released the VRAM info, which they never used to allow to be visible to software other than the driver. nVidia Surround reports as 2GB in monitoring software on my 2GB GTX460s, not 4GB.

Interesting, though.

[tig2575]

I thought VRAM was not doubled when you put two cards in CF / SLI. Each GPU must address its own VRAM, so if you have two cards with 3GB each, you have 3GB total addressable VRAM. Am I mistaken?

edit: to qualify my aspirations for my system - I'm okay with not being able to ratchet AA all the way up to 8x, my primary goal is to have the highest quality lighting and textures, and then to worry about things like AF and AA. Does that give me more leeway for investing in VRAM?

[Tanuki]

VRAM is mirrored in SLI and Crossfire. Which is why those 3gb dual GPU boards are not as great as they sound. They only use 1.5GB per gpu.

Newer games can use VRAM dynamically depending on how much you have. So a game might use up almost all of your 1GB VRAM but put in a 2GB card and its usage doubles.

If you are playing and lacking VRAM you will know fast.

[tig2575]

If you are playing and lacking VRAM you will know fast.

I'm well aware of that - my entire goal is to avoid that from happening :P