What does x8 or x16 mean? In reference to sli

[shinigami321]

Hi, I was reading a similar thread to this but am still confused. I understand that the number has something to do with how fast data can move, but does using multiple cards split this number? I am looking at this motherboard http://us.msi.com/product/mb/Z97-GAMING-7.html#hero-specification It boasts 3 pci x16 slots. So does that mean that it could run 3 cards in sli with no throttling? Also, I hear people talk about 4 way sli but no boards seem to have that many slots. Not that I'm really planning to get that many cards I'm just curious. Sorry I'm a massive noob, and thanks in advance.

 

[Vahe Bro A]

you are correct. but what you have to understand is that most CPU's have 16 PCI lanes. So when you have 1 graphics card on the CPU can support it running at X16 because the CPU has 16 lanes. Once you do SLI the data has to be slit in half so the CPU with 16 PCI lanes can read both cards at x8 x8. the new 2011v3 CPU's can support up to 40 PCI express lanes.

 

[drtoast]

Or using plx chips to double signals you can run 2 cards in x16 or 4 in x8.

The z97 gaming gt has 4 slots to run in 8x8x8x8... four slot boards are just expensive :3

 

[smorizio]

for the 4 way sli there used to be server mb that were made for it they were e-atx mb. they had two server cpu on them and you needed a case with 10 pci slots. one issue also to read up on is that most modern video cards can not send more data over one of the pci lanes faster then today cpu can read. look at the pci 3.0 and the newer pci 4.0 standard that out it show what the max speed is per lane for both. sata ssd now are hiting the bandwith limit of sata chipsets. that why you see the m2 and newer pci 4x controller chipset for sata.

 

[Vahe Bro A]

Or using plx chips to double signals you can run 2 cards in x16 or 4 in x8.

The z97 gaming gt has 4 slots to run in 8x8x8x8... four slot boards are just expensive :3

Agreed unless it has a PLX PEX chip. like the new X99 motherboards have them and some high end 1150.
Asrock uses these chips on their motherboard.

i have a Asrock Fatal1ty Z68 Professional Gen3 1155 socket. it has PLX PEX8608 on it

 

[shinigami321]

So then how do I know if a cpu is one that can handle more lanes? I'm not sure what 2011 v3 represents. Also how much of a performance loss is there if you you split the lanes to 8x +8x or 8x+4x+4x?

 

[Vahe Bro A]

it doesn't lose performance. you are just adding more memory/CUDA cores to your application when you SLI but the cards data transfer rate get's slip in half because the CPU has to read 2 cards now.