How do PCI Lanes work?

[grind]

So, hello guyze.

 

I was watching a benchmark video on single cards vs sli/crossfire, and the cards were scaling really well. After some time I realized that the test bench included one of the new i7s, the one that has a maximum of 40 pci lanes or something like that.

 

That made me think for a while. The cards will always run at the maximum capacity they can, on the test rig of the video they were probably running at x16 x16. But in older systems we see single cards running at x16, and dual cards at x8 x8.

 

How does this difference in bandwidth translates into daily performance? Will an older system have a similar performance scaling as the test rig of the video or will it be chopped down a bit?

 

I tried to search for something like this, but there's one thing I read that made it all a little bit more difficult. I don't understand much about this, and I don't know much about the performance of the nvidia cards, but I read that the scaling of the AMD cards by the time this video was released was really good due to the release of a new driver which improved performance or something like it. So I don't know if comparing this benchmarks to an older benchmark, done with an i7 4790k or another processor with less availability of PCI Lanes will result in the answer I want.

 

Anyways thanks for the help

 

btw, video I was referring to:

 

ps: Now that I think of it, my title may be a little misleading, since that's not my actual question, but now I can't change it

ps²: Thanks to whoever moved my topic, i was unsure on where to put it since it's something about motherboards but i'm talking about gpus and such

[j.dirona]

 

Hope these help ya out

[MegaDave91]

The difference between 8x and 16x is negligible at worst. Don't stress if your cards can't run at 16x and instead 8x. 

 

Even with a single card, 4x is fine as well, but slightly less performance. Nvidia does not allow 4x SLI though.

[Glenwing]

PCIe 3.0 x4 and above is enough bandwidth that it doesn't impact performance, not in gaming anyway.

[laxer]

PCIe 3.0 x4 and above is enough bandwidth that it doesn't impact performance, not in gaming anyway.

to add to this PCIe 2.0 x8 is equivalent and more than enough bandwidth for consumer cards.

[grind]

Yup, I think that does it. I have watched both of the videos before but I didnt remember of them, thanks very much for the help

 

This actually makes me want a second graphics card haha

 

And just for the sake of curiousity, what kind or card would really benefit from the bandwidth of a PCI 3.0 x16 slot?

[Glenwing]

Yup, I think that does it. I have watched both of the videos before but I didnt remember of them, thanks very much for the help

 

This actually makes me want a second graphics card haha

 

And just for the sake of curiousity, what kind or card would really benefit from the bandwidth of a PCI 3.0 x16 slot?

 

None in existence right now would come close to needing that for gaming.  In compute applications, where the GPU is being used to accelerate CPU computations, 3.0 x16 is important since there is a lot more communication between the CPU and GPU and it uses much more PCIe bandwidth than in gaming.