Stoopid Question for you all, sorry in advance.

[cruxamity]

Ok ok, looking to build a system, like everyone else, but there is something I just don't get.

PCI e.

When running one card, it's x16
When running two cards, it's x8, x8.

The dumb question is: Is that the norm? Are there any boards that will run more than one card x16? Does that even exist?

Does the x8, x8 degrade performance of the SLI/Xfire? What exactly does it do to the overall performance? I mean, lower number = bad, right? That's the preschool logic I'm working on.

Could someone clue me in on this part of technology? Or link me to an article so I know what I'm looking at when selecting a motherboard for my build.

Thanks guys

 

[FallenSniper]

Depending on the chipset and the motherboard, some boards only have 16 total lanes to work with. So if you run one card, you use x16. If running two, it splits the load to x8 each. Techically the x8 could bottleneck your cards, and in reality it will decrease SLI/Crossfire performance slightly. For a new build I wouldn't recommend starting with Crossfire/SLI. Buy one more powerful card now rather than two kinda powerful cards, then you can add another card later to get more performance if necessary. You can save a lot of money that way.

 

[paperfox]

intel's lga 1366 slot motherboards can do dual x16 pcie slots even up to four of them but they are much more costly.

x8,x8 dose have some performance loss in sli/xfire, but not that much (yull be fine sub 30" monitor resolution).

this is a review that spicificaly explores the difference between dual x16 and dual x8 over the i7, i5, C2Q, and phenomII CPUs.
http://www.tomshardware.co.uk/core-i5-gaming,review-31673.html

hope this helps!

 

[Mousemonkey]

Personally I only entertain x16 + x16 motherboards in my SLi rigs.

 

[FallenSniper]

I think if I was planning on an SLI or Crossfire build I would make sure it has dual x16... just because

 

[The_Blood_Raven]

At this point, you won't notice much of a hit from x8/x8 at all, though if you add a third or fourth card running x8 bandwidth then you will basically lose all your advantage. Today, it doesn't matter. However tomorrow might be different, I am personally waiting to see how 2 of the various 5xxx series GPUs scale on i5 with its x8/x8 bandwidth before saying either way.

In all honesty, I have used both and I find that the difference is overhyped and hard to judge because you ARE changing parts of the system, meaning any benchmark is not up to scientific standards because more than 1 variable has changed.

 

[cruxamity]

Thanks guys. That helps. When looking for a board, how can you tell if it breaks down the pci e to x8 x8? I see most of the time it will show in the product description, so is it safe to assume that if it does not specifically mention the x8 x8 breakdown, that both channels are x16?

 

[The_Blood_Raven]

No, not at all. It is safe to assume that if it doesn't say x16/x16 or x8/x8 then it is NOT x16/x16, but likely x16/x8, x16/x4, x8/x8, x8/x4 or something even worse. If you must, look up reviews and the board on the manufacturer's actual site for more information.