Why is the 4 GFX cards the "limit" in SLI/Crossfire

[marat569]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

[ZetZet]

it's just cuz there are no mobos.

[dadasmithywinkle]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

 

The performance goes downhill after 3 and after 4 there really is such little gain that you'd be throwing money in the trash. 

[Octavialicious]

not sure if this is why, but most games don't even use over 2 anyways

[terrytek]

There isn't enough slots, and plus, you'd run into bandwidth issues.

[target39]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

Software limitations/PCIe bus limitations and such. I've seen a rig run 8 GPU's with four 7990's before, but it probably wasn't used for gaming. Only rendering and mining machines would benefit from over 4 GPU's. I think NVIDIA's current SLI limit is five GPU's, but I may be wrong.

[TheKDub]

Lack of PCIe slots, not enough bandwidth, not worth it, going from 3 cards in sli/cf to 4 cards in sli/cf has little benefit, so 4 to 5 would have even less.

[minibois]

AFter 3 cards, the results dont go any higher.

So there's no need for it for consumers really.

(In gaming at least.. Maybe for PIXAR or something it would be helpful. I do believe some 6 way SLI PC's exist)

[marat569]

The performance goes downhill after 3 and after 4 there really is such little gain that you'd be throwing money in the trash. 

 

You say that to origin and their 20k rigs! If swifty can have 9 monitors in ifinity, we can have a mobo with an extra chromozone (I mean PCIe slot).

 

We know it goes lower from two, but there are still neckbeards/uber rich peoplethat buy the 3000 waterforce kits (windforce is the shit, waterforce is to steal rich people's money [+1]), origin computers that are 10k+, people will still buy shit for the 3 extra FPS or extra 3dmark points for the 3dmark hall of fame.

 

Personally if I had 30k to just spend like nothing happened, I'd buy a origin for 20k with the best in slot everything.

 

 

There isn't enough slots, and plus, you'd run into bandwidth issues.

 

I just like your avatar

[marat569]

AFter 3 cards, the results dont go any higher.

So there's no need for it for consumers really.

(In gaming at least.. Maybe for PIXAR or something it would be helpful. I do believe some 6 way SLI PC's exist)

 

The 3dmark top 10 would disagree; +1fps is worth 10,000$ to them, just to wave their epenor of pixels.

[Guest DollarPC]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

The human race has still not been able to create a board which can such handle the power of 5 GPU TECHNOLOGY> Illuminati Confirmed 

[Jarsky]

Theres not enough PCI-Express lanes for them to communicate over for more than 4.

 

4 x 8x PCi-E lanes is 32 PCI-E lanes.

You could make it 5, but then thats 40 which is the maximum on a Haswell-E CPU, and it would leave no spare PCI-E for anything else to communicate. 

 

PCI-Express is essentially the backbone of your motherboard, and it allows your processor to talk to everything else like your SATA, and other PCI-E cards.

Earlier boards like Z77 could get around the lower limits in the day by adding 8 more PCI-E lanes via a bridge called a PLX Bridge/Chip.

 

Even before Haswell-E, 4 GPU's wasnt worth it, as they would drop down to 4x, so you would get diminishing returns. Essentially you had very little FPS gain over 3-way.

[Ceatra]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

Who should it be 

 

 

illuminati

[target39]

Here's the PC with four watercooled 7990's (no risers) and dual LGA2011 Xeons if anyone's interested.

http://devgurus.amd.com/message/1284618

[dadasmithywinkle]

You say that to origin and their 20k rigs! If swifty can have 9 monitors in ifinity, we can have a mobo with an extra chromozone (I mean PCIe slot).

 

We know it goes lower from two, but there are still neckbeards/uber rich peoplethat buy the 3000 waterforce kits (windforce is the shit, waterforce is to steal rich people's money [+1]), origin computers that are 10k+, people will still buy shit for the 3 extra FPS or extra 3dmark points for the 3dmark hall of fame.

 

Personally if I had 30k to just spend like nothing happened, I'd buy a origin for 20k with the best in slot everything.

 

 

 

I just like your avatar

 

If I had $30k to spend, I'd build my own. Or a few of my own.

[Ceatra]

But you can't 4 way a Titan Z... why?

 

EDIT: the limit is in 4 GPU's not in 4 Graphics Cards, right? Because a Graphics card can have 2 GPU's... like the Titan Z and the 7970

[Jarsky]

AFter 3 cards, the results dont go any higher.

So there's no need for it for consumers really.

(In gaming at least.. Maybe for PIXAR or something it would be helpful. I do believe some 6 way SLI PC's exist)

 

Incorrect. They do not run in SLI. They use them independantly in GPGPU configurations for crunching data, much like a bitcoin miner. This is common in Universities and Science/medical research institutes.

The results do go higher if you have a Haswell-E with 40 PCIe lanes, and modern games with 4-way SLI on X99 with the appropriate CPU can get just as much gain from 4-way as 3-way and 2-way.

You would get very little, to no performance increase on say a Z97 though as they only have ~28 lanes so you would be running x8/x8/x4/x4

[Godlygamer23]

not sure if this is why, but most games don't even use over 2 anyways

I disagree. They just don't use more than two to the fullest.

[Maslofski]

But you can't 4 way a Titan Z... why?

 

because their dual cards, 1 titan Z = 2 GPUs, so 2 titan Zs = 4 GPUs, and 4 way SLI is the limit

[007agentHP]

current gen cpus an only support 4. the 5930k only has 40 pcie lane support. when you run 4 of them in sli, they take up 32. and good luck finding a motherboard that has support for 5 pci e 16x slots.

[Godlygamer23]

Why is there a limit of a maximum of 4 graphics cards that you can put in SLI/Crossfire? In theory why not just get a mobo that has a 5th PCIe slot (none exist, but if they did), and slap another one in there.

 

Is there a reason four is the max? I did some youtubing but nothing came up?

 

Why not get a case the size of my floor to the roof, a 12 foot motherboard, and get 50way SLI? 

I know that example in silly, but why stop at 4? UNLESS

 

a triangle has 3 sides, 1 eye, 3+1 =4, 4way SLI, illuminati confirmed

 

Really though, who made this magical maximum of "4 gpus"

The scaling would be awful anyways. Anything above two way starts to suffer from bad scaling.

[APrettyCoolWalrus]

There aren't enough slots in the motherboard.

 

Oh and it's 2015, enough of these "Illuminati confirmed" jokes

[ViruZ_HUN]

it's just cuz there are no mobos.

I doubt that. It is because there is no technology to support it yet.

 

IF it was just to extend the mobo, manufacturers would already have done that. Also there is MBs which have 5x PCIE 16x slots and they could put 5 watercooled GPUs under eachother but it is not supported.

 

There is also other issues to stop it like simply "It is not needed and cards is raising with smaller and smaller preformence.

 

2 way SLI: around 40-50% more preformence

 

3 way: 50-60% more preformence

 

4 way : 60-70% more...

 

This is just some simplified statistics, It also depends what cards and what test

[Octavialicious]

I disagree. They just don't use more than two to the fullest.

that's kinda what I was saying.... jeez

[AMICLG]

There isn't enough slots, and plus, you'd run into bandwidth issues.

Bandwidth is fine, depending on the motherboard and if the Gpu is liquid cooled and i/o is single slot; PCI-E slots are a problem either. The problem is scaling, after two GPUs scaling is horrible.