PCI Express Lanes?

[stuckinasquare3]

I was looking at the board here (http://www.newegg.com/Product/Produc...82E16813128545) and it says it has 3 PCI 3.0 x16 slots, but then says x16, x8, and x4 in parenthesis. What does that mean? If I have this board and run 3 cards in SLI do they all run at x16 or do they all run slower? I don't know much about PCI Express and SLI and how they work together, so I'm hoping someone can point me in the right direction.

Thanks!

 

[MagnusTheBrewer]

I was looking at the board here (http://www.newegg.com/Product/Produc...82E16813128545) and it says it has 3 PCI 3.0 x16 slots, but then says x16, x8, and x4 in parenthesis. What does that mean? If I have this board and run 3 cards in SLI do they all run at x16 or do they all run slower? I don't know much about PCI Express and SLI and how they work together, so I'm hoping someone can point me in the right direction.

Thanks!

According to the manual, all three slots share the available lanes. So, if you have one GPU (in the right slot) you get 16x. If you have two GPU's, you get 8x + 8x. If you have three GPU's, you get 8x + 8x + 4x. There are other caveats to consider. If you're using a single monitor, you'd rarely notice any difference between 16x and 4x. If you're using multiple monitors, you would rarely notice any difference with two GPU's running at up to 8x. With three Gpu's and multiple monitors, you MAY notice some degradation of video using that board. Bottom line, more is not always better.

 

[stuckinasquare3]

Is there such a thing as three x16 slots?

 

[ViRGE]

Is there such a thing as three x16 slots?

Not really. Even Sandy Bridge-E only has 40 native lanes. At some point you have to split the bandwidth, either via directly splitting the lanes or by using a bridge chip.

 

[stuckinasquare3]

So what's the best board out right now that would support 3 way sli with the least performance hit?

 

[cmdrdredd]

Well, once you start using a PLX chip you introduce latency. That cannot be avoided. So I'd say they're all the same (as long as they have the PLX bridge chip).

 

[MrWizzard]

According to the manual, all three slots share the available lanes. So, if you have one GPU (in the right slot) you get 16x. If you have two GPU's, you get 8x + 8x. If you have three GPU's, you get 8x + 8x + 4x. There are other caveats to consider. If you're using a single monitor, you'd rarely notice any difference between 16x and 4x. If you're using multiple monitors, you would rarely notice any difference with two GPU's running at up to 8x. With three Gpu's and multiple monitors, you MAY notice some degradation of video using that board. Bottom line, more is not always better.

OP you will be fine, the impact to FPS is so small it's almost not worth bringing up.

Take a look at the bottom most graph, PCIE 3 X16 VS X4.

http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/19.html

 

[stuckinasquare3]

So basically today's cards can't utilize pcie3 x16 as it is so today it doesn't actually matter. But someday it might matter and you'd need a plx chip to get extra x16 lanes. Is that it?

 

[MagnusTheBrewer]

So basically today's cards can't utilize pcie3 x16 as it is so today it doesn't actually matter. But someday it might matter and you'd need a plx chip to get extra x16 lanes. Is that it?

Basically, yes. Look how long pcie 16x has been out and gpu's come nowhere near saturating it. By the time GPU's have progressed to the point of needing a faster bus, there will be an entirely new architecture to deal with it. So, don't worry about it. There was a reason I used the word "rarely" and capitalized "may."

 

[greenhawk]

So basically today's cards can't utilize pcie3 x16 as it is so today it doesn't actually matter. But someday it might matter and you'd need a plx chip to get extra x16 lanes. Is that it?

by the time you would need a plx chip, intel will either have a faster pci-e setup (as the 16x,8x/8x,8x/4x/4x is part of the ivy bridge cpu).

not worth worrying about, as to get a plx chip you will need a new board to get the feature and in all liklyhood, a new cpu anyway, so even when it is needed, you will need a full upgrade to take advantange of it.

best not to worry and get what works for you now with what is available.

 

[Ferzerp]

According to the manual, all three slots share the available lanes. So, if you have one GPU (in the right slot) you get 16x. If you have two GPU's, you get 8x + 8x. If you have three GPU's, you get 8x + 8x + 4x. There are other caveats to consider. If you're using a single monitor, you'd rarely notice any difference between 16x and 4x. If you're using multiple monitors, you would rarely notice any difference with two GPU's running at up to 8x. With three Gpu's and multiple monitors, you MAY notice some degradation of video using that board. Bottom line, more is not always better.

8/4/4 actually.