How does SLI/Crossfire actually work?

[OldWorld]

Hey guys, I was just intrigued how SLI/Crossfire actually worked? So you've got a new graphics card, you plug it into your computer. You connect wire to the back of your card that connects to your screen. Oh wait, you've got two cards! You plug the other one in, then what? You can only put one wire in the back of your monitor, what happens to the other?

Cheers.

 

[enemy1g]

You only need one connection to the monitor from your main (should be the top one) GPU. The only time you would need two connections is if you're using a 4K monitor, I believe.

 

[OldWorld]

So you just slot the other card in, and it'll work?

 

[cball1311]

When you have two GPUs setup for SLI/CrossFire, they are linked together by a ribbon cable. Then, all you have to do is plug the monitor into the top GPU.

 

[rgd1101]

the other card is use for processing. on sli/crossfire, the gpus share the workload between the # of card.

 

[woodbine77]

There is a crossfire cable that connects one gpu to the other which comes with your gpu. Then you enable crossfire in Catalyst Control Centre (at least this is the software I use for AMD).

 

[cball1311]

the other card is use for processing. on sli/crossfire, the gpus share the workload between the # of card.

Yes, to add to that. If you have two GPUs with 2GB vRAM each, the memory does not compound. You still only have 2GB of vRAM available.

 

[enemy1g]

You install the second card like you would the first. Remove the metal brackets, usually two, plug the GPU in, plug in the necessary PCI-E power cables, put on the SLI bridge, boot your PC up, and remember to enable SLI in the Nvidia control panel.

 

[cball1311]

There is a crossfire cable that connects one gpu to the other which comes with your gpu. Then you enable crossfire in Catalyst Control Centre (at least this is the software I use for AMD).

This is a little bit false. The SLI/CrossFire bridge will come with your SLI/CrossFire compatible motherboard, not the GPU.

 

[dottorrent]

Scale Link Interface (SLI / Crossfire) is a bridging interface first used in the 3dFX voodoo cards. It transmitted a signal to the other card which makes it think it is still one card and produce better results. Today's versions still give a signal to the other card to connect to the main card for more power to games and applications, only AMD's crossfire 2.0 (found in the R9 290, 290X and 295X2) now uses the PCI-e slots to transmit the signal.