Max number of GPU graphic cards on a motherboard

[spaolo]

It may be a silly question, but I was thinking, as the title suggest, is there a limit to the max number of graphic cards a motherboard can take?

Beside the "depending on the number of slots", heat, PC case or PSU power..

Scenario:
Asus Deluxe x99 motherboard (5 x PCIe x16)
Custom made chassis (imagine this could accommodate and cool as many card as one's wish)
this splitter:

http://amfeltec.com/products/flexible-x4-pci-express-4-way-splitter-gpu-oriented/

I understand loss of performance as the bandwidth is limited, but, theoretically speaking, could this mobo have 20 graphic cards and work consistently & smoothly? (5 PCIe x 4 splitters)

Not considering the reliability of the splitter, of course; imagine that won't fail.

What about software? Would Windows 8.1 Pro have any problems handling that many cards? Is there a software limitation?

 

[ss202sl]

4 is the max for SLI or Crossfire.
http://support.amd.com/en-us/search/faq/107
http://www.geforce.com/hardware/technology/sli/faq

 

[spaolo]

Thanks. I should have specified "independent graphic cards" not SLI or CF.

Also, considering a CPU with 40 lanes if that makes any difference. Once again, I understand that each of the 20 GPU would only have 2 lanes. I believe the minimum is 4 per device (but I might be wrong) so in that sense they may not communicate all at the same time and that's fine for the scope of this question.

 

[Shaun o]

Graphics cards or any hardware never communicate at the same time anyway.
No matter if you have 2 cards running or 4.

Because of the nature a cpu works at.

It switches at a very rapid rate between the use of other hardware components of the PC.

You only have to look at a bitcoin mining setup, or read about it to get the information you require.
It is one of the most common setups you will find for a Multi Gpu system.

Other than the other use of setting up a render farm where multiple Gpu`s are used for such things as 3D design and modelling creation with something like Lightwave, or 3D`s max rendering and graphics creation software. Cgi or animation.

Along with multiple cpu server boards where up to four Xeon cpu can be used that can have 12 or 16 cpu cores for each processor.

By then your into tens of thousands of pounds for a system setup of that configuration.
Then you have to work out or consider how the whole rig or setup is powered.

And it is often also linked via a very fast internal network setup also.
Or each is optically connected, as a network.
Between the configured server farms.

 

[spaolo]

Graphics cards or any hardware never communicate at the same time anyway.
No matter if you have 2 cards running or 4.

Because of the nature a cpu works at.

It switches at a very rapid rate between the use of other hardware components of the PC.

You only have to look at a bitcoin mining setup, or read about it to get the information you require.
It is one of the most common setups you will find for a Multi Gpu system.

Other than the other use of setting up a render farm where multiple Gpu`s are used for such things as 3D design and modelling creation with something like Lightwave, or 3D`s max rendering and graphics creation software. Cgi or animation.

Along with multiple cpu server boards where up to four Xeon cpu can be used that can have 12 or 16 cpu cores for each processor.

By then your into tens of thousands of pounds for a system setup of that configuration.
Then you have to work out or consider how the whole rig or setup is powered.

And it is often also linked via a very fast internal network setup also.
Or each is optically connected, as a network.
Between the configured server farms.

Hi Shaun, well spotted, wasn't thinking about the electrical input, silly of me! Ofcourse! They are just fast, not simultaneously Thanks for that.

I understand and I did look at mining rigs for answers but I can't find one with 20 GPU's on a single mobo.. If you could point at some link, that would greatly help.

Also I am no considering one of those £10000's server systems.

I would like just to know if with a retail motherboard such as the Deluxe (and splitting PCIe slots) you can connect 20 GPU's, that's all.

As for the CPU a Xeon v3 12 cores if that helps at all.

As for PSU, two AX1200i should suffice as the cards will run slightly undervolted at stock using 75 watts each and I would use PCIe splitters on the power supply as well (the corsair AX1200I states it can provide up to 40A per connector.. therefore that should work.. or will it not? Two cards per connector will absorb 20A at most together)