2x GTX 680 2GB Direct Cu II in SLI or 1x Sapphire AMD Radeon HD 7990 6GB?

[Eckdayz]

Which is better for a 60-60-60 and a 0-240-0 setup?

[SAV1OUR]

sli 680's 

[TheKDub]

Why 680s? why not 770s?

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16814121770

 

Lower price and a slight bit more powerful.

[austin541]

Why 680s? why not 770s?

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16814121770

 

Lower price and a slight bit more powerful.

he already has a 680.

[I/O]

Why 680s? why not 770s?

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16814121770

 

Lower price and a slight bit more powerful.

280x .. lower price and a bit more powerful plus DMA engine CFX scaling is the best in class.

[Askew]

If you've already got a 680 then I'd just add another.

[Lord Pantaloons]

If you've already got a 680 then I'd just add another.

^^This, there's almost no performance difference between a 680 and a 770(minor spec differences) just add another 680 and you're set.

 

 

FYI the 7990 isn't a 6GB card, sure there's 6GB of VRAM on the PCB but it's split between the two GPU's so only 3GB is actually usable.

[I/O]

^^This, there's almost no performance difference between a 680 and a 770(minor spec differences) just add another 680 and you're set.

 

 

FYI the 7990 isn't a 6GB card, sure there's 6GB of VRAM on the PCB but it's split between the two GPU's so only 3GB is actually usable.

Yes it's split but what most people fail to recognize is that each GPU only has to render half the frames that it normally would have to on it's own therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames.

[Askew]

Yes it's split but what most people fail to recognize is that each GPU only has to render half the frames that it normally would have to on it's own therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames.

 

That's the stupidest thing I've read today, the whole point of using 2 gpus is to increase the total number of frames rendered.

[I/O]

That's the stupidest thing I've read today, the whole point of using 2 gpus is to increase the total number of frames rendered.

That's what I said. 2 GPUs in theory split the workload therefore increasing the rate at which frames are displayed aka frame rate or FPS. Nothing stupid about what I posted rather you just did not understand. I need to use better wording or it's just all together over your head not sure which one.

[Askew]

That's what I said. 2 GPUs in theory split the workload therefore increasing the frame rate. Nothing stupid about what I posted rather you just did not understand. I need to use better wording or it's just all together over your head not sure which one.

 

The memory is not pooled, it is connected 3GB to one GPU's controller and half to the other, each GPU's memory controller can only access it's allocated memory and can never store more than 3GB in memory allocated to the other GPU.

 

There is 6GB of memory on the card because there are 2 GPUs on it with 3GB each.

 

VRAM does not stack in any multiple GPU configuration, and due to them rendering alternate frames the data in the memory for each GPU is going to be pretty much the same.

 

Framerate does not change the amount of data in the frame buffer.

[Lord Pantaloons]

Yes it's split but what most people fail to recognize is that each GPU only has to render half the frames that it normally would have to on it's own therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames.

You're trolling, stop you're so bad at it.

[I/O]

You're trolling, stop you're so bad at it.

What ?

[Lord Pantaloons]

What ?

LTT has done several videos on the subject and there have been innumerable threads about SLI/Xfire and VRAM and all that crap on this forum often on a daily basis. There is no way you can actually be under the assumption that Xfire/SLI works like that so I say that you're trolling. If in fact you aren't you should re-evaluate whether you should be giving advice on matters that you "think" that you know about.

[I/O]

The memory is not pooled, it is connected 3GB to one GPU's controller and half to the other, each GPU's memory controller can only access it's allocated memory and can never store more than 3GB in memory allocated to the other GPU.

 

There is 6GB of memory on the card because there are 2 GPUs on it with 3GB each.

 

VRAM does not stack in any multiple GPU configuration, and due to them rendering alternate frames the data in the memory for each GPU is going to be pretty much the same.

 

Framerate does not change the amount of data in the frame buffer.

I never said or implied that vram stacks cause it does not stack. Having 2 GPUs in SLI/CFX shares the workload equally in theory so hence one 3gb Vram GPU renders half the frames and the other 3gb Vram GPU renders the other half of the frames therefore it is like having virtually 6gb of vram. Alternate Frame Rendering it the scientific word for using dual GPUs. The technique is that one graphics processing unit computes all the odd video frames, the other renders the even frames. 3gb Vram for every odd frame and 3gb Vram for every even frame not 3gb for all frames but half of them for a total of 6gb Vram.

[I/O]

LTT has done several videos on the subject and there have been innumerable threads about SLI/Xfire and VRAM and all that crap on this forum often on a daily basis. There is no way you can actually be under the assumption that Xfire/SLI works like that so I say that you're trolling. If in fact you aren't you should re-evaluate whether you should be giving advice on matters that you "think" that you know about.

Now I got it ... you don't understand how CFX/SLI works. Sit tight and have a listen and you might learn a thing or 2 bout and thing or 2 ;-)

[Askew]

I never said or implied that vram stacks cause it does not stack. Having 2 GPUs in SLI/CFX shares the workload equally in theory so hence one 3gb Vram GPU renders half the frames and the other 3gb Vram GPU renders the other half of the frames therefore it is like having virtually 6gb of vram.

 

Framerate does not change the amount of data in the frame buffer, each GPU does not render half of a frame, they render alternate entire frames.

[Lord Pantaloons]

I never said or implied that vram stacks cause it does not stack. Having 2 GPUs in SLI/CFX shares the workload equally in theory so hence one 3gb Vram GPU renders half the frames and the other 3gb Vram GPU renders the other half of the frames therefore it is like having virtually 6gb of vram.

In theory yes that is how it should work, in reality it does not in fact work like that. Take it from someone currently running a dual GPU system.

 

You are wrong(about VRAM, not alternate frame rendering) saying "therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames." implies that it stacks which is does not.

[Askew]

In theory yes that is how it should work, in reality it does not in fact work like that. Take it from someone currently running a dual GPU system.

 

You are wrong(about VRAM, not alternate frame rendering) saying "therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames." implies that it stacks which is does not.

 

Maybe he thinks both GPUs work on the same frame.

[soaringchicken]

7990 cause it looks so awesome to me, would kill to get one.

[I/O]

In theory yes that is how it should work, in reality it does not in fact work like that. Take it from someone currently running a dual GPU system.

 

You are wrong(about VRAM, not alternate frame rendering) saying "therefore even though the Vram is only 3gb per GPU it works like 6gb Vram because each GPU only has to work on half a of the frames." implies that it stacks which is does not.

Alternate Frame Rendering or SLI/CFX it the scientific word for using dual GPUs. The technique is that one graphics processing unit computes all the odd video frames, the other renders the even frames. 3gb Vram for every odd frame and 3gb Vram for every even frame not 3gb for all frames but half of them for a total of 6gb Vram.

[Lord Pantaloons]

Maybe he thinks both GPUs work on the same frame.

He couldn't though because as you can see he went back and edited one of his posts elaborating on the alternate frame rendering. What he fails to see though is that each card can only call upon it's individual supply of VRAM to render its allocated frame. GPU 1 has 2GB of VRAM to render frame A, GPU 2 has 2GB of VRAM to render frame B and the process repeats. If a frame calls for more than the amount of VRAM that a card has there's nothing that can be done to give it more. The cards are operating in the same way that a single card does and have the same drawbacks if they run out of VRAM.

[Lord Pantaloons]

Alternate Frame Rendering or SLI/CFX it the scientific word for using dual GPUs. The technique is that one graphics processing unit computes all the odd video frames, the other renders the even frames. 3gb Vram for every odd frame and 3gb Vram for every even frame not 3gb for all frames but half of them for a total of 6gb Vram.

You're missing the point, yes there is physically 6GB of RAM in the system but each GPU can only use 3GB to draw a frame so there is "only" 3GB in the system.

[I/O]

You're missing the point, yes there is physically 6GB of RAM in the system but each GPU can only use 3GB to draw a frame so there is "only" 3GB in the system.

All 6GB Vram is used just not for each frame. GPU1 renders the first frame with a full 3GB vram and then GPU2 renders the second frame with a full 3GB vram.

[Askew]

All 6GB Vram is used just not for each frame. GPU1 renders the first frame with a full 3GB vram and then GPU2 renders the second frame with a full 3GB vram.

 

You have just contradicted your whole line of debate up to this point, a full 3GB, not 6, at no points does either GPU get to use more than 3GB.

 

I'm done here as it's become clear you don't know what you're talking about.