Can 2gb 680 sli with 4gb 680 ?

rossiboy001 · 14 Sep 2012 at 10:47

I know the answer prob will be no , as im aware it is with previous models , though some people say cards have in the past , just with the smaller VRam of the two cards .
just ordered a 4gb 680 as wanted it for a project 120 hz 3d surround i was planning on putting together .
Just a quick confirmation , that it will not work with the 2gb i have , if thats the case its fine ill move it on or put in our second machine as wanted to upgrade that anyway .

andybird123 · 14 Sep 2012 at 10:50

unless you are going to be getting 3 or 4 680 4GB's I would cancel the 4GB order and just get 2 2GB 680's

the 4GB won't work at all with the 2GB, and there are a couple of SLI 2 card users showing that you run out of GPU grunt way before VRAM even at 3 screen 3D settings

selling outside of the MM is also frowned upon so you might want to edit that bit of your post off before a mod sees it

rossiboy001 · 14 Sep 2012 at 11:08

andybird123 said:
unless you are going to be getting 3 or 4 680 4GB's I would cancel the 4GB order and just get 2 2GB 680's

the 4GB won't work at all with the 2GB, and there are a couple of SLI 2 card users showing that you run out of GPU grunt way before VRAM even at 3 screen 3D settings

selling outside of the MM is also frowned upon so you might want to edit that bit of your post off before a mod sees it

Thanks Andi , So what yr saying is the 2gb will surfice , for 3 screens and you would still have to turn down the eyecandy anyway ? , Is this the case also for 7970"s in crossfire ? , n thanks for the tip .

Gripen90 · 14 Sep 2012 at 11:22

Well it will actually run, but the 4GB card will only utilize 2GB vram because it's synched with the 2GB card.

Rusty0611 · 14 Sep 2012 at 11:25

rossiboy001 said:
Thanks Andi , So what yr saying is the 2gb will surfice , for 3 screens and you would still have to turn down the eyecandy anyway ? , Is this the case also for 7970"s in crossfire ? , n thanks for the tip .

Yes in some games and yes 7970's the same.

bemaniac · 14 Sep 2012 at 11:26

This is all fine in theory until metro last light comes out.

rossiboy001 · 14 Sep 2012 at 11:51

Gripen90 said:
Well it will actually run, but the 4GB card will only utilize 2GB vram because it's synched with the 2GB card.

Thats what i thought ,
Also iv seen this question here in the past , but dont know how relevent the answers were , maybe things have moved on with the current generation .
I was going for a 690 but weighing things up 2x 680"s seem to be better , for the extra vram , and of course you can get one at a time plus slightly better performance , just a little extra lecci is the downside ,
Im currently using 3 27 inch screens in 60hz ,it is my plan to upgrade them , and is a peace by peace project .
When i brought the 2gb I only had one screen and no plans to expand , upgrade ect , such is life .
Even at the current set up , I dont expect to utilize 4gb of vram , im sure 3gb or even 2.5 gb vram would have been enough . but i know im on the edge , wanting to future proof a little as stuff tips over the 2gb barrier .

Gregster · 14 Sep 2012 at 12:01

I was similar to you OP and I now run 3*27" 3D screens with 2*680. My findings were that 2GB is enough (even with all bells and whistles on in BF3). The biggest problem I have is GPU grunt @ 5760*1080. With all bells and whistles in some games, I find the frame rate too low (low 30's at times in BF3).

rossiboy001 · 14 Sep 2012 at 12:09

gregster said:
I was similar to you OP and I now run 3*27" 3D screens with 2*680. My findings were that 2GB is enough (even with all bells and whistles on in BF3). The biggest problem I have is GPU grunt @ 5760*1080. With all bells and whistles in some games, I find the frame rate too low (low 30's at times in BF3).

Maybe I am wrong , but that from research , many opinion is thats when your hitting you Vram wall , and FPS sinks . though just turning enough down of the game settings , below the 2gb threshold will see those framerates jump back up .
Of course there is a limit to what the GPU can process , 4GB will prob be way to much , but i dont see any games needing that much for some time , but where 4gb cards single and sli i think will come into their own is just above that 2gb limit where they wont be bottlenecked , and of course as the game ect utilizes more of the vram , then the performance will drop off ect .
But one or 2 680"s with custom cooling and overclocked , should be able to take advantage of some of that vram .
thats just how i see it .

Gregster · 14 Sep 2012 at 12:26

I did some extensive testing:

http://forums.overclockers.co.uk/showthread.php?t=18433231

This shows that VRAM is plenty with 2GB but the frame rate will only improve by turning settings down.

andybird123 · 14 Sep 2012 at 13:09

Gripen90 said:
Well it will actually run, but the 4GB card will only utilize 2GB vram because it's synched with the 2GB card.

This isn't true... The option for this hasn't existed since gtx 2** series

Rusty0611 · 14 Sep 2012 at 13:29

rossiboy001 said:
Maybe I am wrong , but that from research , many opinion is thats when your hitting you Vram wall , and FPS sinks . though just turning enough down of the game settings , below the 2gb threshold will see those framerates jump back up .
Of course there is a limit to what the GPU can process , 4GB will prob be way to much , but i dont see any games needing that much for some time , but where 4gb cards single and sli i think will come into their own is just above that 2gb limit where they wont be bottlenecked , and of course as the game ect utilizes more of the vram , then the performance will drop off ect .
But one or 2 680"s with custom cooling and overclocked , should be able to take advantage of some of that vram .
thats just how i see it .

If you want to run max settings in BF3 (the biggest GPU/VRAM hog) then you can run this at 5760*1080 with no VRAM slowdowns. You will be close to the 2GB threshold however crucially you will be under it. The extra VRAM only benefits when you're running out of it of course...

Now frame rates at these maximum settings are quite low minimums/averages. Definitely low enough to impact on gameplay. The issue is that even 2 heavily overclocked 680's do not have enough GPU horsepower to run the settings at this resolution. VRAM amount isn't coming into it. If these settings were using 1500MB of VRAM gameplay would still suffer.

So to get a balance of a decent frame rate and a pleasing level of image quality you have to drop settings and as such you drastically lower the VRAM requirements well away from what can be considered close.

At a balance of Full Ultra without MSAA my average FPS is in the 100's with minimums in the 70's. VRAM is around 1500MB. Realistically I have 500MB of VRAM 'spare' to play with on settings which provide a smooth experience.

MSAA is just too expensive to run on 3 monitors unless you're using 3 of this generations top GPU's.

If you've heard otherwise on this - they're wrong.

Rusty0611 · 14 Sep 2012 at 13:35

(FXAA provides an acceptable compromise between image quality/performance when you don't have the GPU grunt to run MSAA across 3 screens)

rossiboy001 · 14 Sep 2012 at 16:47

Thanks Rusty , some food for thought , But yeah i did expect the performance to drop as your vram use increases , Though not as much as your findings around the 2gb cap .

Just on the issue of pairing them (not that it is my main plan) but an option . I found this since researching today from the nvidia website .

"Can I mix and match graphics cards with different sizes of memory?

When purchasing a second graphics card, you should try to match the memory size so that you are ensured full value and performance from your purchase. However, while it is not recommended, NVIDIA does offer the flexibility to run graphics cards with different sized memory by using CoolBits. Using CoolBits (value set to 18), you can force both of the cards to use the lower of the two memory sizes and operate them together in SLI mode. When dissimilar memory sizes are enabled to work together using CoolBits, the effective memory size for each card becomes the smaller of the memory sizes."

link
http://www.geforce.com/hardware/technology/sli/faq#c19

Gregster · 14 Sep 2012 at 16:52

http://www.************.co.uk/forums/showthread.php?16515-Installing-a-new-Graphics-Card/page3

I wasn't sure on this and still not sure. I was led to believe it was a 'no go' for modern day cards.

Rusty0611 · 14 Sep 2012 at 17:04

rossiboy001 said:
Thanks Rusty , some food for thought , But yeah i did expect the performance to drop as your vram use increases , Though not as much as your findings around the 2gb cap .

Just to be clear - the performance isn't dropping off because VRAM is close to maximum... it is dropping off because MSAA is a resource hog on the GPU's.

As I said, if MSAA max settings used 1500MB of VRAM I would still get the same framerate.

whyscotty · 14 Sep 2012 at 17:04

Rusty0611 said:
MSAA is just too expensive to run on 3 monitors unless you're using 3 of this generations top GPU's.

If you've heard otherwise on this - they're wrong.

+1

rossiboy001 · 14 Sep 2012 at 17:06

gregster said:
http://www.************.co.uk/forums/showthread.php?16515-Installing-a-new-Graphics-Card/page3

I wasn't sure on this and still not sure. I was led to believe it was a 'no go' for modern day cards.

Yeah its very mixed , maybe ill send them an email to confirm , though i dont know how long if ever they will get back . Bit odd though to have it up if that stopped 3 years ago as some suggest .

Just on this sli and surround business there"s not a lot to go on , through the other forums and youtube . Its all peoples opinions , just not any who actually say " I have and i am" or " I tried" ect

Gregster · 14 Sep 2012 at 17:18

rossiboy001 said:
Yeah its very mixed , maybe ill send them an email to confirm , though i dont know how long if ever they will get back . Bit odd though to have it up if that stopped 3 years ago as some suggest .

Just on this sli and surround business there"s not a lot to go on , through the other forums and youtube . Its all peoples opinions , just not any who actually say " I have and i am" or " I tried" ect

lol me and Rusty both have surround and have done some extensive testing. Mine was a 20 minute bench on each of the 5 games in 3D and non 3D.

Also to confirm what Rusty is saying, if the games with low fps only used 120mb, it would still only produce the same fps as in that graph. Settings will need to be turned down from ultra to get playable fps. VRAM is not the issue here, it is GPU grunt.

rossiboy001 · 14 Sep 2012 at 17:41

Cheers , so what yr concluding , is the only market for a higher than 2GB card would be with a 3 way setup at current top range 680 or prob 7970 cards . Until the next generation perhaps .
That graph is good thanks , It be nice to see a comparison with 2x4gb cards all the same .

Because , TBH im coming around to your conclusions , But another View is could this be somehow software/driver related which will mature (eventually)
Something else must be going on , cause it does not make full sense that one GPU can handle a standard 2GB of card ram , yet two GPU"S together cant manage the ram fully of one card of 2GB , let alone more , putting aside the full 4 GB argument .
What this says in a way is your get better graphics with one card , but better FPS with two , if that makes sense .

Or another way to interperete , For example ,One card will give you say 30FPS , two cards will give you 58FPS , but even if you were to drop to 30FPS , you couldnt still turn up the candy .
Therefore for many if you get playable framerates , there is no benefit at all going sli or crossfire .