Question about the 8x 16x pci-e lanes

[unkn0wnhacka]

I have this motherboard.. I just now noticed that it has 4 16x slots and ive heard people talking alot about the new cards being able to run at 16x each.

Im not really sure what all this means.. i was wondering if someone could help me understand.
Ive never used CF or SLI before so im kind of lost.
Is this a good motherboard? :)

http://www.newegg.com/Product/Product.aspx?Item=N82E16813130223

[DedEmbryonicCe1]

For general background, some 16x slots are 16x physically but not 16x electrically. In some cases they are permanently stuck at 8x and in others they share some PCI-E lanes with another slot and auto-switch between 8x and 16x depending on how many other slots are occupied*.

As to your board:

4 x PCI Express 2.0 x16

Slot configurations:
Dual CrossFire (16X+16X)
Quad CrossFire (8X+8X+8X+8X)
That means with two slots occupied by video cards it can do 16x + 16x and with all four occupied each slot has to drop down to 8x because of the limited number of PCI-E lanes (electrically!) that connect to the 790FX chipset. 790FX boards can also do 16x + 8x + 8x in a tri-crossfire configuration.

*For the 790GX and other chipsets with only 16x or 8x + 8x configurations sometimes a paddle card must be placed in the unoccupied slot to make the other run at 16x in single card setups.

[Asylum1]

That seems to be a good board you have.
It will do 16x+16x in crossfire.
But in doesnt support SLI
Crossfire is for ATI cards.

[AH64]

I have the 790fx-gd70 and its a great board, I would pick it up if i were you.

[unkn0wnhacka]

I have that board already lol :)

I know this isnt an SLI board.. i just bought this card until the 5870x2 comes out. I was going to return it (thanks to newegg for letting me) but i decided ill just wait till the x2 comes out and sell the 295 to a friend :)
I might not even use the crossfire.. who knows.. maybe someday a game would need a few 5870x2's in CF lol

[AceNZ]

Maybe it will be different with the new ATI 5xxx cards, but for the current generation, PCIe 2.0 x16 doesn't buy you any additional performance compared to x8, which in turn is only moderately more than x4.

The number of PCIe lanes available actually has more impact on disk I/O than video, for the current generation of controllers.

[Zehnsucht]

Maybe it will be different with the new ATI 5xxx cards, but for the current generation, PCIe 2.0 x16 doesn't buy you any additional performance compared to x8, which in turn is only moderately more than x4.

The number of PCIe lanes available actually has more impact on disk I/O than video, for the current generation of controllers.

You are correct, the difference between PCIe 2.0 8x and 16x is negligible:

http://techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/

[zanzabar]

I have that board already lol :)

I know this isnt an SLI board.. i just bought this card until the 5870x2 comes out. I was going to return it (thanks to newegg for letting me) but i decided ill just wait till the x2 comes out and sell the 295 to a friend :)
I might not even use the crossfire.. who knows.. maybe someday a game would need a few 5870x2's in CF lol

what happens with the gd70 is that if u have pci-e slots 1 and 4 in use then they are in 16x but if u use something in pci-e slots 3 or 5 then it will change all of the 16x slots to 8x. (slot 2 is a 1x and comes from the SB so it dosnt effect the other slots)

and i wouldent recommend a dual gpu card on an 8x slot thats like a 4x for each gpu. and instead of waiting for an x2 u could get 4 cards they will fit

[Computurd]

you will not see the x8 hinder your gpu speed UNLESS you are in crossfire/sli