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GPU Vram usage

Soldato
Joined
18 May 2003
Posts
4,884
Firstly whilst I've got a background in hardware and software I don't have any knowledge of the inner workings of GPU vram so I'd appreciate someone with commercial knowledge of such to correct me and add to this thread.


There's been a lot of discussion of whether 1GB/2GB/3GB etc is enough Vram at various resolutions/games, people typically use things like afterburner to measure peak vram usage and then claim on the forum that as GameX uses 2GB of vram on their GPU then that is the minimum needed.

I suspect that such claims are bogus and video cards, much like modern O/S, use as much ram as they can and having less vram than a card would use in GameX doesn't necessarily reduce performance at all.


My reasoning is this, I suspect that a modern GPU will continually load textures/data into Vram without bothering to clean up old/unused data unless it has to, ie it has run out of vram and needs to load new data.

If the above is true then even though a game may use 2.5GB in total, as long as you have say 2GB there could be no performance difference.

Of course the tipping point comes when a game needs say 2GB of ram to render the current scene and a card only has say 1.5GB, at this point we see a nose dive on frame rates as Vram has data continually swapping out to render the scene.


As I said at the start I don't have in depth knowledge of how Vram is managed so I'm interested to hear opinions from people who have a commercial knowledge of such things.
 
Soldato
Joined
3 Feb 2012
Posts
14,431
Location
Peterborough
There was a thread just recently that discussed this. I'm on my iPhone so can't link easily but I think the general outcome was that 1GB is pushing it at 1920*1080 but OK at 1680*1050.

1.5GB was OK currently for 1080p but on the limit. 2GB was fine for 1080p and 1200p and borderline ok for 1440p / eyefinity set ups. 3GB is fine for all.

No hard scientific analysis but that's the previous thread summed up. I'm sure someone will link for your perusal
 
Associate
Joined
1 Jan 2007
Posts
1,103
well i feel the same as you rusty, i read posts about people saying that all the time, and think to myself well i have no problems with my setup, which is gtx480 sli 1.5 gb, i play bf3 at 2560 x 1600 on my 30" dell, and my vram gets darn close the max but never goes above what is available, i have no stutters and the games runs at a smooth rate( between 50 -65 fps depending on the map) in multiplayer mode, i have everything on ultra except aa which is at 4x, as i dont see any difference above that due to the high resolution which has less jaggies to start with.
 
Caporegime
Joined
26 Dec 2003
Posts
25,675
I'm yet to see benchmarks of a 1.5GB card tanking in anything other than Eyefinity type resolutions so I put it all down to hysteria and those with the slower 2-3GB cards justifying their purchase, if the arguments about VRAM were valid then a GTX580 1.5GB wouldn't still be consistently beating ATI's 2GB cards or 2.5GB GTX570's.

Most people seem to be of the belief that whatever is stored in VRAM is what's being used at that exact moment but like straxusii explained it's just a storage area, a GPU is unlikely to clear out unused data/textures from memory unless it gets full and needs to make space so all of the "my 3GB card uses 2.5GB in x game therefore 1.5GB is not enough" claims are meaningless.

If 1.5GB is not enough then we should have seen drastic reductions in benchmark performance by now.
 
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Associate
Joined
22 Jan 2005
Posts
1,266
Location
Australia
With a 5870 with 1gb at 1200p, with AA used in many games (not bf3), I haven't had any vram related issues.
 
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