Why does SLI require a special motherboard? (don't guess)

[JoostinOnline]

Question in the title. Given that it uses a bridge instead of PCIe lanes to communicate, it seems like the it wouldn't require anything special, or that it wound at least be more common than Crossfire support.

 

Edit: Please no more guesses.

[Fasauceome]

If I had to guess, it's the same reason Optane has to have it's own certified slot. "Optane ready" wouldn't really be that hard to enable, just like StoreMI. On the one hand, it's an artificial price barrier, but on the other, chances are you aren't buying two grapics cards if you can't afford an appropriate high end motherboard as well. On the plus side, I feel as though it's become a little easier to tell when SLI is available. 

[Ashley MLP Fangirl]

if i had to guess it would be that you need at least two x16 slots that can run at x16 speed at the same time. not all boards can run all slots at full speed at the same time. 

 

EDIT: that's also becuase of the cpu lane limitations on most consumer chips. 

[ahuckphin]

Because Nvidia 

[JoostinOnline]

6 minutes ago, fasauceome said:

If I had to guess, it's the same reason Optane has to have it's own certified slot. "Optane ready" wouldn't really be that hard to enable, just like StoreMI. On the one hand, it's an artificial price barrier, but on the other, chances are you aren't buying two grapics cards if you can't afford an appropriate high end motherboard as well. On the plus side, I feel as though it's become a little easier to tell when SLI is available. 

There's probably some kind of added tech, but I'd like to know what it is.

2 minutes ago, firelighter487 said:

if i had to guess it would be that you need at least two x16 slots that can run at x16 speed at the same time. not all boards can run all slots at full speed at the same time. 

 

EDIT: that's also becuase of the cpu lane limitations on most consumer chips. 

SLI runs fine in 8x mode. A 16 lane CPU can do 2-way SLI, but not more. Support for higher configurations is dead now anyway.

1 minute ago, bindydad123 said:

Because Nvidia 

That's not really helpful.

[PlayStation 2]

iF i HaD tO gUeSs

From what I've gathered, it basically has to do with needing the required chipset that can send data between the two cards in an SLI setup.

[wojtepanik]

It requires nvidia certification to have sli enabled, crossfire works on any mobo with pci-e 3.0

[porina]

Bandwidth. Before Turing, the SLI bridge gave 1 or 2 GB/s depending on version (from memory). PCIe 3.0 is roughly 1 GB/s per lane. So at the minimum 8x per card requirement, the bulk of available bandwidth is vis PCIe. There may be some other considerations, like only using GPU lanes and not chipset lanes which would immediately bottleneck you.

 

With Turing nvlink gives 50GB/s so way more than before. Maybe they still keep the PCIe requirement as it is still available bandwidth.

[Bananasplit_00]

needs NVIDIA certified, that costs a lot of money to do

[JoostinOnline]

2 minutes ago, Bananasplit_00 said:

needs NVIDIA certified, that costs a lot of money to do

Can you provide a source for that?

[xAcid9]

INNM, SLI certification need 8x 8x minimum on both slot. CFX don't have that requirement, you can enable CFX on mainboard with 8x 4x which that 4x lane came from Northbridge and not directly from processor, that sometime produce crappy frametimes and best to avoid CFX-ing

[Bananasplit_00]

1 hour ago, JoostinOnline said:

Can you provide a source for that?

https://m.ign.com/articles/2004/11/11/nvidias-sli-certification-and-logo-program

 

That's from when it started, 14 years ago and here is their inquiry page:

https://www.nvidia.com/object/sli_certification_inquiry.html

 

It's a bit hard to find anything that isn't old af though because it's nothing new 

[Turtle Rig]

This is why you look at the box when you buy the card and it should say SLI ready and what not.

[JoostinOnline]

20 hours ago, Bananasplit_00 said:

https://m.ign.com/articles/2004/11/11/nvidias-sli-certification-and-logo-program

 

That's from when it started, 14 years ago and here is their inquiry page:

https://www.nvidia.com/object/sli_certification_inquiry.html

 

It's a bit hard to find anything that isn't old af though because it's nothing new 

So basically "nobody but NVIDIA and manufacturers know" XD