Sli/ Crossfire limitations

[Flame_of_Orion]

I was wondering why are multi gpu set ups are limited to four gpu cores, is this because of a hardware limitation, or has it been determined by Nvidia/ AMD?

[xnoobftw]

I was wondering why are multi gpu set ups are limited to four gpu cores, is this because of a hardware limitation, or has it been determined by Nvidia/ AMD?

Because there really isnt a point in going more than 4 due to diminishing returns

[nsyedhasan]

Because we do not have the CPU lanes to actually drive them in some cases. Also buying more than 3 GPUs is considered to have bad value, buying more than 4 would be even worse.

[Enderman]

1) You would have limited bandwidth of PCIe lanes divided into too many cards.

2) Multi-GPU sacling is horrible after 3 cards. In most cases 4 cards actually performs worse than 3.

3) Very few motherboards would be able to fir 5 dual slot PCIe lanes

4) So few people do quad-SLI/CFX that adding more cards would bring in no money.

[Flame_of_Orion]

Because we do not have the CPU lanes to actually drive them in some cases. Also buying more than 3 GPUs is considered to have bad value, buying more than 4 would be even worse.

Thanks, I did believe it was a limitation on the Pcie lane bandwith provided currently, I understand that scaling is poor beyond to GPUs. I simply wanted reassurance.

[Cheddle]

I would be interested to see a comparison between 4 x r9 290x's and 2 x r9 295x's