Really Dumb Newbie Like Question

[xMotivee]

Alright guys, so I watched Linus' video multiple times on Dual GPU's.  I understand that if you have 2 GPU's that you don't have double the RAM, so please explain to me what exactly the purpose is in using 2 graphics cards.  Please keep it in dummy terms so that I can thoroughly understand it all :lol:

[DarkBlade2117]

Think of a 4x4 car/truck.

You get more traction, but no more horsepower.

Same goes for GPU. More horsepower, same vRam

[Imabigmac]

More calculation/processing power

[stupidhuman]

Alright guys, so I watched Linus' video multiple times on Dual GPU's.  I understand that if you have 2 GPU's that you don't have double the RAM, so please explain to me what exactly the purpose is in using 2 graphics cards.  Please keep it in dummy terms so that I can thoroughly understand it all :lol:

Because VRAM isn't everything.

[Sam Z Man]

Because you double your GPU compute power, adding more ram to stuff don't always make a difference.

[Lord_Karango17]

You doubly the computation speed, but they both have to store the textures needed for the game, so your vram stay the same.

 

If games scaled perfectly, and you were not near your vram limit, then adding another gpu would theoretically double your fps.

[Aereldor]

Think of it as two horses pulling a wagon. You won't go twice as fast because you have two horses instead of one. What you will get is an ability to haul more people in the wagon, equating to FPS. Similarly, if one of the horses is a slowpoke, adding a super-speedy steed beside him isn't going to make him pick up his pace- if you have a 2GB video card and a 4GB video card in crossfire (NVidia SLI doesn't allow this), you still have effectively 2GB of VRAM.

I don't know a whole lot about this, but the way dual-GPU technology works doesn't let it combine the VRAM of both cards into a single gigantic pool, but operates at the highest level made available by a single GPU, and uses the graphics processors on both cards to perform calculations faster, as opposed to a single one.

 

[Knaj]

Think of it as two horses pulling a wagon. You won't go twice as fast because you have two horses instead of one. What you will get is an ability to haul more people in the wagon, equating to FPS. Similarly, if one of the horses is a slowpoke, adding a super-speedy steed beside him isn't going to make him pick up his pace- similarly, if you have a 2GB video card and a 4GB video card in crossfire, you still have effectively 2GB of VRAM.

I don't know a whole lot about this, but the way dual-GPU technology works doesn't let it combine the VRAM of both cards into a single gigantic pool, but operates at the highest level made available by a single GPU, and uses the graphics processors on both cards to perform calculations faster, as opposed to a single one.

 

 

Two horses pulling a wagon... That's a very good analogy.. 

[xMotivee]

Think of a 4x4 car/truck.

You get more traction, but no more horsepower.

Same goes for GPU. More horsepower, same vRam

Thank you, that actually makes sense!! haha

[lxyfutures]

It's about the price. For example in Amazon a GTX950 will cost you like 150$, if you sli it, you can get two GTX950 by 300$ .And according to Linus's video ,it performs better than a single GTX970 which will cost you around 320$. So this is it... And there's more. If you use a case with side panel, you will find dual GPU looks awsome. And if you have only one GPU that's OK ,but not so sexy

[Rylie59]

vram certainly isn't the only thing about a gpu. Having two gpus combine their power. You get a good boost in fps because now you have two cards being able to do work instead of one. Though of course you don't get exactly twice the performance one one card. In general, the next tier card is a better deal than two lower tier cards.

[Aereldor]

Two horses pulling a wagon... That's a very good analogy.. 

Took me a while to find something. I went through everything from rowing teams to pizza toppings.

[Tangtawan]

the VRAM is RAM of the GPU itself.

 

If you have two cards, you have two sets of GPU and two sets of VRAM.. each set of VRAM works for its own GPU.

[TheCaptain53]

It's about the price. For example in Amazon a GTX950 will cost you like 150$, if you sli it, you can get two GTX950 by 300$ .And according to Linus's video ,it performs better than a single GTX970 which will cost you around 320$. So this is it... And there's more. If you use a case with side panel, you will find dual GPU looks awsome. And if you have only one GPU that's OK ,but not so sexy

That's not really the whole story, though, is it?

With any multiple GPU setup there are inherent drawbacks, the first of which is compatibility. For video games and applications, it's up to the game developers and graphics card makers to implement SLI/Xfire profiles, and if there isn't one, the second card does sweet fuck all. Just sits there looking subjectively pretty.

As said before, with 2x 2GB graphics card, you still only have a usable pool of 2GB. So whilst SLI GTX 950s may be more powerful than a GTX 970, the VRAM limitation makes going for a multiple GPU setup with low or mid-end hardware a bad idea. 

Another drawback is increased heat output and power consumption. A single GTX 970 will consume less power and output less heat than two GTX 950s. 

You can also get micro-stuttering when the graphics cards aren't in sync.

And possibly one of the biggest issues with multi-GPU setups is that performance does not increase on a 1:1 scale with the number of GPUs. For example, if you have one card that can output a game at 30 fps, adding a second card won't push it to 60 fps. More in the realms of 45-50 fps. This is also dependant on the effort of game developers and video card makers. Furthermore, this is the reason most people don't recommend more than a two-way graphics card setup, because you start to experience diminishing returns as the number of graphics cards increases.

I totally get multiple GPU setups for high-end to enthusiast grade hardware, for example, doing a Xfire setup of R9 390(X)s. This makes sense, and for really demanding scenarios like 4K Ultra @ 60 fps in the latest AAA titles, an SLI/Xfire setup is pretty much the only way to achieve this. However, for low-end hardware, there's really not much point unless you got the second card for really cheap.

[lxyfutures]

That's not really the whole story, though, is it?

With any multiple GPU setup there are inherent drawbacks, the first of which is compatibility. For video games and applications, it's up to the game developers and graphics card makers to implement SLI/Xfire profiles, and if there isn't one, the second card does sweet fuck all. Just sits there looking subjectively pretty.

As said before, with 2x 2GB graphics card, you still only have a usable pool of 2GB. So whilst SLI GTX 950s may be more powerful than a GTX 970, the VRAM limitation makes going for a multiple GPU setup with low or mid-end hardware a bad idea. 

Another drawback is increased heat output and power consumption. A single GTX 970 will consume less power and output less heat than two GTX 950s. 

You can also get micro-stuttering when the graphics cards aren't in sync.

And possibly one of the biggest issues with multi-GPU setups is that performance does not increase on a 1:1 scale with the number of GPUs. For example, if you have one card that can output a game at 30 fps, adding a second card won't push it to 60 fps. More in the realms of 45-50 fps. This is also dependant on the effort of game developers and video card makers. Furthermore, this is the reason most people don't recommend more than a two-way graphics card setup, because you start to experience diminishing returns as the number of graphics cards increases.

I totally get multiple GPU setups for high-end to enthusiast grade hardware, for example, doing a Xfire setup of R9 390(X)s. This makes sense, and for really demanding scenarios like 4K Ultra @ 60 fps in the latest AAA titles, an SLI/Xfire setup is pretty much the only way to achieve this. However, for low-end hardware, there's really not much point unless you got the second card for really cheap.

Yes man，you are totally right about this...There are some drawback